Patent Document

TECHNICAL FIELD  
         [0001]    The present invention relates to a family of power transmissions having two input clutches which selectively connect an input shaft to first and second pairs of planetary gear sets to provide at least five forward speed ratios and 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.  
           [0003]    A primary focus of transmission and engine design work is in the area of increasing vehicle fuel efficiency. Manual transmissions typically provide improved vehicle fuel economy over automatic transmissions because automatic transmissions use a torque converter for vehicle launch and multiple plate hydraulically-applied clutches for gear engagement. Clutches of this type, left unengaged or idling, impose a parasitic drag torque on a drive line due to the viscous shearing action which exists between the plates and discs rotating at different speeds relative to one another. This drag torque adversely affects vehicle fuel economy for automatic transmissions. Also, the hydraulic pump that generates the pressure needed for operating the above-described clutches further reduces fuel efficiency associated with automatic transmissions. Manual transmissions eliminate these problems.  
           [0004]    While manual transmissions are not subject to the above described fuel efficiency related problems, manual transmissions typically provide poor shift quality because a significant torque interruption is required during each gear shift as the engine is disengaged from the transmission by the clutch to allow shafts rotating at different speeds to be synchronized.  
           [0005]    So called “automated manual” transmissions provide electronic shifting in a manual transmission configuration which, in certain circumstances, improves fuel efficiency by eliminating the parasitic losses associated with the torque converter and hydraulic pump needed for clutching. Like manual transmissions, a drawback of automated manual transmissions is that the shift quality is not as high as an automatic transmission because of the torque interruption during shifting.  
           [0006]    So called “dual-clutch automatic” transmissions also eliminate the torque converter and replace hydraulic clutches with synchronizers but they go further to provide gear shift quality which is superior to the automated manual transmission and similar to the conventional automatic transmission, which makes them quite attractive. However, most known dual-clutch automatic transmissions include a lay shaft or countershaft gear arrangement, and have not been widely applied in vehicles because of their complexity, size and cost. For example, a dual clutch lay shaft transmission could require eight sets of gears, two input/shift clutches and seven synchronizers/dog clutches to provide six forward speed ratios and a reverse speed ratio. An example of a dual-clutch automatic transmission is described in U.S. Pat. No. 5,385,064, which is hereby incorporated by reference.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention provides a low content multi-speed dual-clutch transmission family utilizing planetary gear sets rather than lay shaft gear arrangements. In particular, the invention includes four planetary gear sets, two input/shift clutches, and eight selectable torque transmitting mechanisms to provide at least six forward speed ratios and a reverse speed ratio.  
           [0008]    According to one aspect of the invention, the family of transmissions has four planetary gear sets, each of which includes a first, second and third member, which members may comprise a sun gear, ring gear, or a planet carrier assembly member.  
           [0009]    In referring to the first, second, third and fourth gear sets in this description and in the claims, these sets may be counted “first” to “fourth” 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, the first member of the first planetary gear set is continuously connected with the first member of the second planetary gear set through a first interconnecting member.  
           [0012]    In yet another aspect of the present invention, another member of the first or second planetary gear set is continuously connected with the first member of the third planetary gear set, the first member of the fourth planetary gear set and with the output shaft through a second interconnecting member.  
           [0013]    In accordance with a further aspect of the invention, a first input clutch selectively connects the input shaft with a member of the first or second planetary gear set.  
           [0014]    In accordance with another aspect of the present invention, a second input clutch selectively connects the input shaft with the second member of the third planetary gear set.  
           [0015]    In another aspect of the invention, first and second torque transmitting mechanisms, such as synchronizers, selectively connect members of the first and second planetary gear sets with other members of the first and second planetary gear sets, or with the first input clutch.  
           [0016]    In still a further aspect of the invention, third and fourth torque transmitting mechanisms, such as synchronizers, selectively connect members of the third planetary gear set with members of the fourth planetary gear set.  
           [0017]    In still another aspect of the invention, fifth and sixth torque transmitting mechanisms, such as brakes, selectively connect members of the first or second planetary gear set with a stationary member (transmission housing).  
           [0018]    In still another aspect of the invention, seventh and eighth torque transmitting mechanisms, such as brakes, selectively connect members of the fourth planetary gear set with the stationary member.  
           [0019]    In accordance with a further aspect of the invention, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of at least three to provide at least six forward speed ratios and a reverse speed ratio.  
           [0020]    In accordance with a further aspect of the invention, the eight torque transmitting mechanisms may comprise synchronizers.  
           [0021]    In accordance with a further aspect of the invention, the first input clutch is applied for odd number speed ranges, and the second input clutch is applied for even number speed ranges, or vice versa.  
           [0022]    In another aspect of the invention, the first input clutch and the second input clutch are interchanged (i.e. alternately engaged) to shift from odd number speed range to even number speed range, or vice versa.  
           [0023]    In accordance with a further aspect of the invention, each selected torque transmitting mechanism for a new speed ratio is engaged prior to shifting of the input clutches to achieve shifts without torque interruptions.  
           [0024]    In accordance with a further aspect of the invention, at least one pair of synchronizers is executed as a double synchronizer to reduce cost and package size.  
           [0025]    In accordance with a further aspect of the invention, at least one of the torque transmitting mechanisms can be eliminated to realize five forward speed ratios and a reverse speed ratio.  
           [0026]    The above objects, features, advantages, 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  
       [0027]    [0027]FIG. 1 a  is a schematic representation of a powertrain including a planetary transmission incorporating a family member of the present invention;  
         [0028]    [0028]FIG. 1 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 1 a;    
         [0029]    [0029]FIG. 2 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0030]    [0030]FIG. 2 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 2 a;    
         [0031]    [0031]FIG. 3 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0032]    [0032]FIG. 3 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 3 a;    
         [0033]    [0033]FIG. 4 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0034]    [0034]FIG. 4 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 4 a;    
         [0035]    [0035]FIG. 5 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0036]    [0036]FIG. 5 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 5 a;    
         [0037]    [0037]FIG. 6 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0038]    [0038]FIG. 6 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 6 a;    
         [0039]    [0039]FIG. 7 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0040]    [0040]FIG. 7 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 7 a;    
         [0041]    [0041]FIG. 8 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0042]    [0042]FIG. 8 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 8 a;    
         [0043]    [0043]FIG. 9 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0044]    [0044]FIG. 9 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 9 a;    
         [0045]    [0045]FIG. 10 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0046]    [0046]FIG. 10 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 10 a;    
         [0047]    FIG. 11 a is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0048]    [0048]FIG. 11 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 11 a;    
         [0049]    [0049]FIG. 12 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0050]    [0050]FIG. 12 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 12 a;    
         [0051]    [0051]FIG. 13 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention;  
         [0052]    [0052]FIG. 13 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 13 a;    
         [0053]    [0053]FIG. 14 a  is a schematic representation of a powertrain having a planetary transmission incorporating another family member of the present invention; and  
         [0054]    [0054]FIG. 14 b  is a truth table and chart depicting some of the operating characteristics of the powertrain shown in FIG. 14 a.   
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0055]    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  12 , a planetary transmission  14 , and a conventional final drive mechanism  16 .  
         [0056]    The planetary transmission  14  includes an input shaft  17  continuously connected with the engine  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 four planetary gear sets  20 ,  30 ,  40  and  50 .  
         [0057]    The planetary gear set  20  includes a sun gear member  22 , a ring gear member  24 , and a planet carrier assembly member  26 . The planet carrier assembly member  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 .  
         [0058]    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 .  
         [0059]    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 .  
         [0060]    The planetary gear set  50  includes a sun gear member  52 , a ring gear member  54 , and a planet carrier assembly member  56 . The planet carrier assembly member  56  includes a plurality of pinion gears  57  rotatably mounted on a carrier member  59  and disposed in meshing relationship with both the sun gear member  52  and the ring gear member  54 .  
         [0061]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  20 ,  30 ,  40  and  50  are divided into first and second transmission subsets  60 ,  61  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  60  includes planetary gear sets  20  and  30 , and transmission subset  61  includes planetary gear sets  40  and  50 . The output shaft  19  is continuously connected with members of both subsets  60  and  61 .  
         [0062]    As mentioned above, the first and second input clutches  62 ,  63  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  60  or transmission subset  61 . The first and second input clutches  62 ,  63  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  60 ,  61  prior to engaging the respective input clutches  62 ,  63 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  64 ,  65 ,  66 ,  67 ,  68 ,  69 ,  70  and  71 . The torque transmitting mechanisms  64 ,  65 ,  68  and  69  comprise braking synchronizers, and the torque transmitting mechanisms  66 ,  67 ,  70  and  71  comprise rotating synchronizers.  
         [0063]    The rotating synchronizers and braking synchronizers are referred to in the claims as follows: first and second torque transmitting mechanisms  66 ,  67 ; third and fourth torque transmitting mechanisms  70 ,  71 ; fifth and sixth torque transmitting mechanisms  64 ,  65 ; and seventh and eighth torque transmitting mechanisms  68 ,  69 . The other family members are similarly referenced in the claims (i.e. rotating synchronizers generally in order of planetary gear sets from left to right in Figures; and braking synchronizers generally in order of planetary gear sets from left to right in Figures).  
         [0064]    By way of example, synchronizers which may be implemented as the rotating and/or braking synchronizers referenced herein are shown in the following patents, each of which are incorporated by reference in their entirety: U.S. Pat. Nos. 5,651,435; 5,975,263; 5,560,461; 5,641,045; 5,497,867; 6,354,416.  
         [0065]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  60 ,  61  (i.e. through the clutch  62  to the sun gear member  22  and through the clutch  63  to the sun gear member  42 ). The ring gear member  24  is continuously connected with the sun gear member  32  through the interconnecting member  72 . The planet carrier assembly member  36  is continuously connected with the planet carrier assembly member  46 , the sun gear member  54  and the output shaft  19  through the interconnecting member  74 .  
         [0066]    The sun gear member  22  is selectively connectable with the input shaft  17  through the input clutch  62 . The sun gear member  42  is selectively connectable with the input shaft  17  through the input clutch  63 . The sun gear member  24  is selectively connectable with the transmission housing  80  through the braking synchronizer  64 . The planet carrier assembly member  26  is selectively connectable with the transmission housing  80  through the braking synchronizer  65 . The planet carrier assembly member  26  is selectively connectable with the ring gear member  34  through the synchronizer  66 . The ring gear member  34  is selectively connectable with the sun gear member  22  through the synchronizer  67 . The planet carrier assembly member  56  is selectively connectable with the transmission housing  80  through the braking synchronizer  68 . The sun gear member  52  is selectively connectable with the transmission housing  80  through the braking synchronizer  69 . The ring gear member  44  is selectively connectable with the planet carrier assembly member  56  through the synchronizer  70 . The ring gear member  44  is selectively connectable with the sun gear member  52  through the synchronizer  71 .  
         [0067]    As shown in FIG. 1 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio.  
         [0068]    The reverse speed ratio is established with the engagement of the input clutch  62 , the braking synchronizer  65  and the synchronizer  66 . The input clutch  62  connects the sun gear member  22  to the input shaft  17 . The braking synchronizer  65  connects the planet carrier assembly member  26  to the transmission housing  80 . The synchronizer  66  connects the planet carrier assembly member  26  to the ring gear member  34 . The sun gear member  22  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  26  and the ring gear member  34  do not rotate. The ring gear member  24  rotates at the same speed as the sun gear member  32 . The ring gear member  24  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The planet carrier assembly member  36  and the planet carrier assembly member  46  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  36 , and therefore the output shaft  19 , 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 numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20 ,  30 .  
         [0069]    The first forward speed ratio is established with the engagement of the input clutch  63 , the braking synchronizer  68  and the synchronizer  71 . The input clutch  63  connects the sun gear member  42  to the input shaft  17 . The braking synchronizer  68  connects the planet carrier assembly member  56  to the transmission housing  80 . The synchronizer  71  connects the ring gear member  44  to the sun gear member  52 . The sun gear member  42  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  46  and the ring gear member  54  rotate at the same speed as the output shaft  19 . The ring gear member  44  rotates at the same speed as the sun gear member  52 . The planet carrier assembly member  46 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  44 , the speed of the sun gear member  42  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The planet carrier assembly member  56  does not rotate. The ring gear member  54  rotates at a speed determined from the speed of the sun gear member  52  and the ring gear/sun gear tooth ratio of the planetary gear set  50 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  40 ,  50 .  
         [0070]    The second forward speed ratio is established with the engagement of the input clutch  62 , the braking synchronizer  64  and the synchronizer  66 . The input clutch  62  connects the sun gear member  22  to the input shaft  17 . The braking synchronizer  64  connects the ring gear member  24  to the transmission housing  80 . The synchronizer  66  connects the ring gear member  34  to the planet carrier assembly member  26 . The sun gear member  22  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  26  rotates at the same speed as the ring gear member  34 . The ring gear member  24  and the sun gear member  32  do not rotate. The planet carrier assembly member  26  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The planet carrier assembly member  36  and the planet carrier assembly member  46  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  36 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  34  and the ring gear/sun gear tooth ratio of the planetary gear set  30 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  20 ,  30 .  
         [0071]    The third forward speed ratio is established with the engagement of the input clutch  63 , the braking synchronizer  68  and the synchronizer  70 . The input clutch  63  connects the sun gear member  42  to the input shaft  17 . The braking synchronizer  68  connects the planet carrier assembly member  56  to the transmission housing  80 . The synchronizer  70  connects the ring gear member  44  to the planet carrier assembly member  56 . The sun gear member  42  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  46  and the ring gear member  54  rotate at the same speed as the output shaft  19 . The ring gear member  44  and the planet carrier assembly member  56  do not rotate. The planet carrier assembly member  46 , and therefore the output shaft  19 , rotates at a speed determined from 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 third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  40 .  
         [0072]    The fourth forward speed ratio is established with the engagement of the input clutch  62 , the braking synchronizer  65  and the synchronizer  67 . The input clutch  62  connects the sun gear member  22  to the input shaft  17 . The braking synchronizer  65  connects the planet carrier assembly member  26  to the transmission housing  80 . The synchronizer  67  connects the sun gear member  22  to the ring gear member  34 . The sun gear member  22  and the ring gear member  34  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  26  does not rotate. The ring gear member  24  rotates at the same speed as the sun gear member  32 . The ring gear member  24  rotates at a speed determined from the speed of the sun gear member  22  and the ring gear/sun gear tooth ratio of the planetary gear set  20 . The planet carrier assembly member  36  and the planet carrier assembly member  46  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  36 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  34 , 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 ratios of the planetary gear sets  20 ,  30 .  
         [0073]    The fifth forward speed ratio is established with the engagement of the input clutch  63 , the braking synchronizer  69  and the synchronizer  70 . The input clutch  63  connects the sun gear member  42  to the input shaft  17 . The braking synchronizer  69  connects the sun gear member  52  to the transmission housing  80 . The synchronizer  70  connects the ring gear member  44  to the planet carrier assembly member  56 . The sun gear member  42  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  46  and the ring gear member  54  rotate at the same speed as the output shaft  19 . The ring gear member  44  rotates at the same speed as the planet carrier assembly member  56 . The planet carrier assembly member  46 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  44 , the speed of the sun gear member  42  and the ring gear/sun gear tooth ratio of the planetary gear set  40 . The sun gear member  52  does not rotate. The ring gear member  54  rotates at a speed determined from the speed of the planet carrier assembly member  56  and the ring gear/sun gear tooth ratio of the planetary gear set  50 . The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  40 ,  50 .  
         [0074]    The sixth forward speed ratio is established with the engagement of the input clutch  62 , and the synchronizers  66 ,  67 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the sixth forward speed ratio is  1 .  
         [0075]    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 R1/S1 value is the tooth ratio of the planetary gear set  20 ; the R2/S2 value is the tooth ratio of the planetary gear set  30 ; the R3/S3 value is the tooth ratio of the planetary gear set  40 ; and the R4/S4 value is the tooth ratio of the planetary gear set  50 . 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 first and second forward speed ratios is 1.76, while the step ratio between the reverse and first forward ratio is −0.76.  
         [0076]    [0076]FIG. 2 a  shows a powertrain  110  having a conventional engine  12 , a planetary transmission  114 , and a conventional final drive mechanism  16 . The planetary transmission  114  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  118 , and an output shaft  19  connected with the final drive mechanism  16 . The planetary gear arrangement  118  includes four planetary gear sets  120 ,  130 ,  140  and  150 .  
         [0077]    The planetary gear set  120  includes a sun gear member  122 , a ring gear member  124 , and a planet carrier assembly member  126 . The planet carrier assembly member  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 .  
         [0078]    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 intermeshing pinion gears  137 ,  138  rotatably mounted on a carrier member  139  and disposed in meshing relationship with the ring gear member  134  and the sun gear member  132 , respectively.  
         [0079]    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 .  
         [0080]    The planetary gear set  150  includes a sun gear member  152 , a ring gear member  154 , and a planet carrier assembly member  156 . The planet carrier assembly member  156  includes a plurality of pinion gears  157  rotatably mounted on a carrier member  159  and disposed in meshing relationship with both the sun gear member  152  and the ring gear member  154 .  
         [0081]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  120 ,  130 ,  140  and  150  are divided into first and second transmission subsets  160 ,  161  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  160  includes planetary gear sets  120  and  130 , and transmission subset  161  includes planetary gear sets  140  and  150 . The output shaft  19  is continuously connected with members of both subsets  160  and  161 .  
         [0082]    As mentioned above, the first and second input clutches  162 ,  163  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  160  or transmission subset  161 . The first and second input clutches  162 ,  163  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  160 ,  161  prior to engaging the respective input clutches  162 ,  163 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  164 ,  165 ,  166 ,  167 ,  168 ,  169 ,  170  and  171 . The torque transmitting mechanisms  164 ,  165 ,  168  and  169  comprise braking synchronizers, and the torque transmitting mechanisms  166 ,  167 ,  170  and  171  comprise rotating synchronizers.  
         [0083]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  160 ,  161  (i.e. through the clutch  162  to the sun gear member  122  and through the clutch  163  to the sun gear member  142 ). The planet carrier assembly member  126  is continuously connected with the sun gear member  132  through the interconnecting member  172 . The ring gear member  134  is continuously connected with the planet carrier assembly member  146 , the ring gear member  154  and the output shaft  19  through the interconnecting member  174 .  
         [0084]    The sun gear member  122  is selectively connectable with the input shaft  17  through the input clutch  162 . The sun gear member  142  is selectively connectable with the input shaft  17  through the input clutch  163 . The planet carrier assembly member  126  is selectively connectable with the transmission housing  180  through the braking synchronizer  164 . The ring gear member  124  is selectively connectable with the transmission housing  180  through the braking synchronizer  165 . The ring gear member  124  is selectively connectable with the planet carrier assembly member  136  through the synchronizer  166 . The sun gear member  122  is selectively connectable with the planet carrier assembly member  136  through the synchronizer  167 . The planet carrier assembly member  156  is selectively connectable with the transmission housing  180  through the braking synchronizer  168 . The sun gear member  152  is selectively connectable with the transmission housing  180  through the braking synchronizer  169 . The ring gear member  144  is selectively connectable with the planet carrier assembly member  156  through the synchronizer  170 . The ring gear member  144  is selectively connectable with the sun gear member  152  through the synchronizer  171 .  
         [0085]    As shown in FIG. 2 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio.  
         [0086]    The reverse speed ratio is established with the engagement of the input clutch  162 , the braking synchronizer  164  and the synchronizer  166 . The input clutch  162  connects the sun gear member  122  to the input shaft  17 . The braking synchronizer  164  connects the planet carrier assembly member  126  to the transmission housing  180 . The synchronizer  166  connects the ring gear member  124  to the planet carrier assembly member  136 . The sun gear member  122  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  126  and the sun gear member  132  do not rotate. The ring gear member  124  rotates at the same speed as the planet carrier assembly member  136 . The ring gear member  124  rotates at a speed determined from the speed of the sun gear member  122  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The ring gear member  134  and the planet carrier assembly member  146  rotate at the same speed as the output shaft  19 . The ring gear member  134 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  136  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear set  120 ,  130 .  
         [0087]    The first forward speed ratio is established with the engagement of the input clutch  163 , the braking synchronizer  168  and the synchronizer  171 . The input clutch  163  connects the sun gear member  142  to the input shaft  17 . The braking synchronizer  168  connects the planet carrier assembly member  156  to the transmission housing  180 . The synchronizer  171  connects the ring gear member  144  to the sun gear member  152 . The sun gear member  142  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  146  and the ring gear member  154  rotate at the same speed as the output shaft  19 . The ring gear member  144  rotates at the same speed as the sun gear member  152 . The planet carrier assembly member  146 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  144 , the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The planet carrier assembly member  156  does not rotate. The ring gear member  154  rotates at a speed determined from the speed of the sun gear member  152  and the ring gear/sun gear tooth ratio of the planetary gear set  150 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear set  140 ,  150 .  
         [0088]    The second forward speed ratio is established with the engagement of the input clutch  162 , the braking synchronizer  165  and the synchronizer  166 . The input clutch  162  connects the sun gear member  122  to the input shaft  17 . The braking synchronizer  165  connects the ring gear member  124  to the transmission housing  180 . The synchronizer  166  connects the ring gear member  124  to the planet carrier assembly member  136 . The sun gear member  122  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  126  rotates at the same speed as the sun gear member  132 . The sun gear member  124  and the planet carrier assembly member  136  do not rotate. The planet carrier assembly member  126  rotates at a speed determined from the speed of the sun gear member  122  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The ring gear member  134  and the planet carrier assembly member  146  rotate at the same speed as the output shaft  19 . The ring gear member  134 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  132  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  120 ,  130 .  
         [0089]    The third forward speed ratio is established with the engagement of the input clutch  163 , the braking synchronizer  168  and the synchronizer  170 . The input clutch  163  connects the sun gear member  142  to the input shaft  17 . The braking synchronizer  168  connects the planet carrier assembly member  156  to the transmission housing  180 . The synchronizer  170  connects the ring gear member  144  to the planet carrier assembly member  156 . The sun gear member  142  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  146  and the ring gear member  154  rotate at the same speed as the output shaft  19 . The ring gear member  144  and the planet carrier assembly member  156  do not rotate. The planet carrier assembly member  146 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  140 .  
         [0090]    The fourth forward speed ratio is established with the engagement of the input clutch  162 , the braking synchronizer  165  and the synchronizer  167 . The input clutch  162  connects the sun gear member  122  to the input shaft  17 . The braking synchronizer  165  connects the ring gear member  124  to the transmission housing  180 . The synchronizer  167  connects the sun gear member  122  to the planet carrier assembly member  136 . The sun gear member  122  and the planet carrier assembly member  136  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  126  rotates at the same speed as the sun gear member  132 . The ring gear member  124  does not rotate. The planet carrier assembly member  126  rotates at a speed determined from the speed of the sun gear member  122  and the ring gear/sun gear tooth ratio of the planetary gear set  120 . The ring gear member  134  and the planet carrier assembly member  146  rotate at the same speed as the output shaft  19 . The ring gear member  134 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the planet carrier assembly member  136 , the speed of the sun gear member  132  and the ring gear/sun gear tooth ratio of the planetary gear set  130 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  120 ,  130 .  
         [0091]    The fifth forward speed ratio is established with the engagement of the input clutch  163 , the braking synchronizer  169  and the synchronizer  170 . The input clutch  163  connects the sun gear member  142  to the input shaft  17 . The braking synchronizer  169  connects the sun gear member  152  to the transmission housing  180 . The synchronizer  170  connects the ring gear member  144  to the planet carrier assembly member  156 . The sun gear member  142  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  146  and the ring gear member  154  rotate at the same speed as the output shaft  19 . The ring gear member  144  rotates at the same speed as the planet carrier assembly member  156 . The planet carrier assembly member  146 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  144 , the speed of the sun gear member  142  and the ring gear/sun gear tooth ratio of the planetary gear set  140 . The sun gear member  152  does not rotate. The ring gear member  154  rotates at a speed determined from the speed of the planet carrier assembly member  156  and the ring gear/sun gear tooth ratio of the planetary gear set  150 . The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  140 ,  150 .  
         [0092]    The sixth forward speed ratio is established with the engagement of the input clutch  162 , and the synchronizers  166 ,  167 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the sixth forward speed ratio is  1 .  
         [0093]    As set forth above, the truth table of FIG. 2 b  describes the engagement sequence of the torque transmitting mechanisms utilized to provide a reverse drive ratio and six 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 R1/S1 value is the tooth ratio of the planetary gear set  120 ; the R2/S2 value is the tooth ratio of the planetary gear set  130 ; the R3/S3 value is the tooth ratio of the planetary gear set  140 ; and the R4/S4 value is the tooth ratio of the planetary gear set  150 . 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. For example, the first to second step ratio is 1.73.  
         [0094]    Turning the FIG. 3 a , a powertrain  210  having a conventional engine  12 , a planetary transmission  214 , and conventional final drive mechanism  16  is shown.  
         [0095]    The planetary transmission  214  includes an input shaft  17  continuously connected with the engine  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 four planetary gear sets  220 ,  230 ,  240  and  250 .  
         [0096]    The planetary gear set  220  includes a sun gear member  222 , a ring gear member  224 , and a planet carrier assembly member  226 . The planet carrier assembly member  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 .  
         [0097]    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 .  
         [0098]    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 .  
         [0099]    The planetary gear set  250  includes a sun gear member  252 , a ring gear member  254 , and a planet carrier assembly member  256 . The planet carrier assembly member  256  includes a plurality of pinion gears  257  rotatably mounted on a carrier member  259  and disposed in meshing relationship with both the sun gear member  252  and the ring gear member  254 .  
         [0100]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  220 ,  230 ,  240  and  250  are divided into first and second transmission subsets  260 ,  261  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  260  includes planetary gear sets  220  and  230 , and transmission subset  261  includes planetary gear sets  240  and  250 . The output shaft  19  is continuously connected with members of both subsets  260  and  261 .  
         [0101]    As mentioned above, the first and second input clutches  262 ,  263  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  260  or transmission subset  261 . The first and second input clutches  262 ,  263  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  260 ,  261  prior to engaging the respective input clutches  262 ,  263 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  264 ,  265 ,  266 ,  267 ,  268 ,  269 ,  270  and  271 . The torque transmitting mechanisms  264 ,  265 ,  268  and  269  comprise braking synchronizers, and the torque transmitting mechanisms  266 ,  267 ,  270  and  271  comprise rotating synchronizers.  
         [0102]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  260 ,  261  (i.e. through the clutch  262  to the sun gear member  222  and through the clutch  263  to the sun gear member  242 ). The ring gear member  224  is continuously connected with the sun gear member  232  through the interconnecting member  272 . The planet carrier assembly member  236  is continuously connected with the planet carrier assembly member  246 , the ring gear member  254  and the output shaft  19  through the interconnecting member  274 .  
         [0103]    The sun gear member  222  is selectively connectable with the input shaft  17  through the input clutch  262 . The sun gear member  242  is selectively connectable with the input shaft  17  through the input clutch  263 . The ring gear member  224  is selectively connectable with the transmission housing  280  through the braking synchronizer  264 . The planet carrier assembly member  226  is selectively connectable with the transmission housing  280  through the braking synchronizer  265 . The sun gear member  222  is selectively connectable with the ring gear member  234  through the synchronizer  266 . The planet carrier assembly member  226  is selectively connectable with the ring gear member  234  through the synchronizer  267 . The planet carrier assembly member  256  is selectively connectable with the transmission housing  280  through the braking synchronizer  268 . The sun gear member  252  is selectively connectable with the transmission housing  280  through the braking synchronizer  269 . The ring gear member  244  is selectively connectable with the planet carrier assembly member  256  through the synchronizer  270 . The ring gear member  244  is selectively connectable with the sun gear member  252  through the synchronizer  271 .  
         [0104]    As shown in FIG. 3 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio.  
         [0105]    The reverse speed ratio is established with the engagement of the input clutch  262 , the braking synchronizer  265  and the synchronizer  267 . The input clutch  262  connects the sun gear member  222  to the input shaft  17 . The braking synchronizer  265  connects the planet carrier assembly member  226  to the transmission housing  280 . The synchronizer  267  connects the planet carrier assembly member  226  to the ring gear member  234 . The sun gear member  222  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  226  and the ring gear member  234  do not rotate. The ring gear member  224  rotates at the same speed as the sun gear member  232 . The ring gear member  224  rotates at a speed determined from the speed of the sun gear member  222  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The planet carrier assembly member  236  and the planet carrier assembly member  246  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  236 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  232  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  220 ,  230 .  
         [0106]    The first forward speed ratio is established with the engagement of the input clutch  263 , the braking synchronizer  268  and the synchronizer  271 . The input clutch  263  connects the sun gear member  242  to the input shaft  17 . The braking synchronizer  268  connects the planet carrier assembly member  256  to the transmission housing  280 . The synchronizer  271  connects the ring gear member  244  to the sun gear member  252 . The sun gear member  242  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  246  and the ring gear member  254  rotate at the same speed as the output shaft  19 . The ring gear member  244  rotates at the same speed as the sun gear member  252 . The planet carrier assembly member  246 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  244 , the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The planet carrier assembly member  256  does not rotate. The ring gear member  254  rotates at a speed determined from the speed of the sun gear member  252  and the ring gear/sun gear tooth ratio of the planetary gear set  250 . The numerical value of the first forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  240 ,  250 .  
         [0107]    The second forward speed ratio is established with the engagement of the input clutch  262 , the braking synchronizer  264  and the synchronizer  267 . The input clutch  262  connects the sun gear member  222  to the input shaft  17 . The braking synchronizer  264  connects the ring gear member  224  to the transmission housing  280 . The synchronizer  267  connects the planet carrier assembly member  226  to the ring gear member  234 . The sun gear member  222  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  226  rotates at the same speed as the ring gear member  234 . The ring gear member  224  and the sun gear member  232  do not rotate. The planet carrier assembly member  226  rotates at a speed determined from the speed of the sun gear member  222  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The planet carrier assembly member  236  and the planet carrier assembly member  246  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  236 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  234  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  220 ,  230 .  
         [0108]    The third forward speed ratio is established with the engagement of the input clutch  263 , the braking synchronizer  268  and the synchronizer  270 . The input clutch  263  connects the sun gear member  242  to the input shaft  17 . The braking synchronizer  268  connects the planet carrier assembly member  256  to the transmission housing  280 . The synchronizer  270  connects the ring gear member  244  to the planet carrier assembly member  256 . The sun gear member  242  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  246  and the ring gear member  254  rotate at the same speed as the output shaft  19 . The ring gear member  244  and the planet carrier assembly member  256  do not rotate. The planet carrier assembly member  246 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  240 .  
         [0109]    The fourth forward speed ratio is established with the engagement of the input clutch  262 , the braking synchronizer  265  and the synchronizer  266 . The input clutch  262  connects the sun gear member  222  to the input shaft  17 . The braking synchronizer  265  connects the planet carrier assembly member  226  to the transmission housing  280 . The synchronizer  266  connects the sun gear member  222  to the ring gear member  234 . The sun gear member  222  and the ring gear member  234  rotate at the same speed as the input shaft  17 . The planet carrier assembly member  226  does not rotate. The ring gear member  224  rotates at the same speed as the sun gear member  232 . The ring gear member  224  rotates at a speed determined from the speed of the sun gear member  222  and the ring gear/sun gear tooth ratio of the planetary gear set  220 . The planet carrier assembly member  236  and the planet carrier assembly member  246  rotate at the same speed as the output shaft  19 . The planet carrier assembly member  236 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  234 , the speed of the sun gear member  232  and the ring gear/sun gear tooth ratio of the planetary gear set  230 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear set  220 ,  230 .  
         [0110]    The fifth forward speed ratio is established with the engagement of the input clutch  263 , the braking synchronizer  269  and the synchronizer  270 . The input clutch  263  connects the sun gear member  242  to the input shaft  17 . The braking synchronizer  269  connects the sun gear member  252  to the transmission housing  280 . The synchronizer  270  connects the ring gear member  244  to the planet carrier assembly member  256 . The sun gear member  242  rotates at the same speed as the input shaft  17 . The planet carrier assembly member  246  and the ring gear member  254  rotate at the same speed as the output shaft  19 . The ring gear member  244  rotates at the same speed as the planet carrier assembly member  256 . The planet carrier assembly member  246 , and therefore the output shaft  19 , rotates at a speed determined from the speed of the ring gear member  244 , the speed of the sun gear member  242  and the ring gear/sun gear tooth ratio of the planetary gear set  240 . The sun gear member  252  does not rotate. The ring gear member  254  rotates at a speed determined from the speed of the planet carrier assembly member  256  and the ring gear/sun gear tooth ratio of the planetary gear set  250 . The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  240 ,  250 .  
         [0111]    The sixth forward speed ratio is established with the engagement of the input clutch  262 , and the synchronizers  266 ,  267 . In this configuration, the input shaft  17  is directly connected to the output shaft  19 . The numerical value of the sixth forward speed ratio is  1 .  
         [0112]    As previously set forth, the truth table of FIG. 3 b  describes the combinations of engagements utilized for six forward speed ratios and one reverse speed ratio. 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 the tooth ratios given in FIG. 3 b . The R1/S1 value is the tooth ratio of the planetary gear set  220 ; the R2/S2 value is the tooth ratio of the planetary gear set  230 ; the R3/S3 value is the tooth ratio of the planetary gear set  240 ; and the R4/S4 value is the tooth ratio of the planetary gear set  250 . Also depicted in FIG. 3 b  is a chart representing the ratio steps between adjacent forward speed ratios and the reverse speed ratio. For example, the first to second ratio interchange has a step of 1.83.  
         [0113]    A powertrain  310 , shown in FIG. 4 a , includes the engine  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  12 , a planetary gear arrangement  318 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  318  includes four planetary gear sets  320 ,  330 ,  340  and  350 .  
         [0114]    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 .  
         [0115]    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 intermeshing pinion gears  337 ,  338  rotatably mounted on a carrier member  339  and disposed in meshing relationship with the ring gear member  334  and the sun gear member  332 , respectively.  
         [0116]    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 .  
         [0117]    The planetary gear set  350  includes a sun gear member  352 , a ring gear member  354 , and a planet carrier assembly member  356 . The planet carrier assembly member  356  includes a plurality of pinion gears  357  rotatably mounted on a carrier member  359  and disposed in meshing relationship with both the sun gear member  352  and the ring gear member  354 .  
         [0118]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  320 ,  330 ,  340  and  350  are divided into first and second transmission subsets  360 ,  361  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  360  includes planetary gear sets  320  and  330 , and transmission subset  361  includes planetary gear sets  340  and  350 . The output shaft  19  is continuously connected with members of both subsets  360  and  361 .  
         [0119]    As mentioned above, the first and second input clutches  362 ,  363  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  360  or transmission subset  361 . The first and second input clutches  362 ,  363  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  360 ,  361  prior to engaging the respective input clutches  362 ,  363 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  364 ,  365 ,  366 ,  367 ,  368 ,  369 ,  370  and  371 . The torque transmitting mechanisms  364 ,  365 ,  368  and  369  comprise braking synchronizers, and the torque transmitting mechanisms  366 ,  367 ,  370  and  371  comprise rotating synchronizers.  
         [0120]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  360 ,  361  (i.e. through the clutch  362  to the sun gear member  322  and through the clutch  363  to the sun gear member  342 ). The ring gear member  324  is continuously connected with the sun gear member  332  through the interconnecting member  372 . The ring gear member  334  is continuously connected with the planet carrier assembly member  346 , the ring gear member  354  and the output shaft  19  through the interconnecting member  374 .  
         [0121]    The sun gear member  322  is selectively connectable with the input shaft  17  through the input clutch  362 . The sun gear member  342  is selectively connectable with the input shaft  17  through the input clutch  363 . The planet carrier assembly member  326  is selectively connectable with the transmission housing  380  through the braking synchronizer  364 . The planet carrier assembly member  336  is selectively connectable with the transmission housing  380  through the braking synchronizer  365 . The sun gear member  322  is selectively connectable with the planet carrier assembly member  336  through the synchronizer  366 . The planet carrier assembly member  326  is selectively connectable with the sun gear member  322  through the synchronizer  367 . The planet carrier assembly member  356  is selectively connectable with the transmission housing  380  through the braking synchronizer  368 . The sun gear member  352  is selectively connectable with the transmission housing  380  through the braking synchronizer  369 . The ring gear member  344  is selectively connectable with the planet carrier assembly member  356  through the synchronizer  370 . The ring gear member  344  is selectively connectable with the sun gear member  352  through the synchronizer  371 .  
         [0122]    The truth tables given in FIGS. 4 b ,  5   b ,  6   b ,  7   b ,  8   b ,  9   b ,  10   b ,  11   b ,  12   b ,  13   b  and  14   b  show the engagement sequences for the torque transmitting mechanisms to provide at least five forward speed ratios and one reverse speed ratio. As shown and described above for the configurations in FIGS. 1 a ,  2   a  and  3   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.  
         [0123]    The truth table shown in FIG. 4 b  describes the engagement combination and engagement sequence necessary to provide the reverse drive ratio and six 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 R1/S1 value is the tooth ratio for the planetary gear set  320 ; the R2/S2 value is the tooth ratio for the planetary gear set  330 ; the R3/S3 value is the tooth ratio for the planetary gear set  340 ; and the R4/S4 value is the tooth ratio for the planetary gear set  350 . 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 1.68.  
         [0124]    Those skilled in the art will recognize that the numerical values of the reverse and second forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  320 ,  330 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  340 ,  350 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  340 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  330 . The numerical value of the sixth forward speed ratio is 1.  
         [0125]    A powertrain  410  shown in FIG. 5 a  includes a conventional engine  12 , a planetary transmission  414 , and a conventional final drive mechanism  16 . The planetary transmission  414  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  418 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  418  includes four planetary gear sets  420 ,  430 ,  440  and  450 .  
         [0126]    The planetary gear set  420  includes a sun gear member  422 , a ring gear member  424 , and a planet carrier assembly member  426 . The planet carrier assembly member  426  includes a plurality of pinion gears  427  rotatably mounted on a carrier member  429  and disposed in meshing relationship with both the sun gear member  422  and the ring gear member  424 .  
         [0127]    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 sun gear member  432  and the ring gear member  434 .  
         [0128]    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 .  
         [0129]    The planetary gear set  450  includes a sun gear member  452 , a ring gear member  454 , and a planet carrier assembly member  456 . The planet carrier assembly member  456  includes a plurality of intermeshing pinion gears  457 ,  458  rotatably mounted on a carrier member  459  and disposed in meshing relationship with the ring gear member  454  and the sun gear member  452 , respectively.  
         [0130]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  420 ,  430 ,  440  and  450  are divided into first and second transmission subsets  460 ,  461  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  460  includes planetary gear sets  420  and  430 , and transmission subset  461  includes planetary gear sets  440  and  450 . The output shaft  19  is continuously connected with members of both subsets  460  and  461 .  
         [0131]    As mentioned above, the first and second input clutches  462 ,  463  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  460  or transmission subset  461 . The first and second input clutches  462 ,  463  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  460 ,  461  prior to engaging the respective input clutches  462 ,  463 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  464 ,  465 ,  466 ,  467 ,  468 ,  469 ,  470  and  471 . The torque transmitting mechanisms  464 ,  465 ,  468  and  469  comprise braking synchronizers, and the torque transmitting mechanisms  466 ,  467 ,  470  and  471  comprise rotating synchronizers.  
         [0132]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  460 ,  461  (i.e. through the clutch  462  to the sun gear member  422  and through the clutch  463  to the sun gear member  442 ). The ring gear member  424  is continuously connected with the sun gear member  432  through the interconnecting member  472 . The ring gear member  434  is continuously connected with the planet carrier assembly member  446 , the ring gear member  454  and the output shaft  19  through the interconnecting member  474 .  
         [0133]    The sun gear member  422  is selectively connectable with the input shaft  17  through the input clutch  462 . The sun gear member  442  is selectively connectable with the input shaft  17  through the input clutch  463 . The planet carrier assembly member  426  is selectively connectable with the transmission housing  480  through the braking synchronizer  464 . The planet carrier assembly member  436  is selectively connectable with the transmission housing  480  through the braking synchronizer  465 . The sun gear member  422  is selectively connectable with the planet carrier assembly member  436  through the synchronizer  466 . The planet carrier assembly member  426  is selectively connectable with the sun gear member  422  through the synchronizer  467 . The planet carrier assembly member  456  is selectively connectable with the transmission housing  480  through the braking synchronizer  468 . The sun gear member  452  is selectively connectable with the transmission housing  480  through the braking synchronizer  469 . The ring gear member  444  is selectively connectable with the planet carrier assembly member  456  through the synchronizer  470 . The ring gear member  444  is selectively connectable with the sun gear member  452  through the synchronizer  471 .  
         [0134]    As shown in FIG. 5 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio.  
         [0135]    [0135]FIG. 5 b  also provides a chart of the ratio steps between adjacent forward ratios and between the reverse and first ratio. For example, the ratio step between the first and second forward ratios is 1.92. Those skilled in the art will recognize that the numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  430 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  420 ,  430 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  440 . The numerical value of the third forward speed ratio is 1. The numerical values of the fourth and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  440 ,  450 .  
         [0136]    A powertrain  510 , shown in FIG. 6 a , includes a conventional engine  12 , a powertrain  514 , and a conventional final drive mechanism  16 . The powertrain  514  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  518 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  518  includes four planetary gear sets  520 ,  530 ,  540  and  550 .  
         [0137]    The planetary gear set  520  includes a sun gear member  522 , a ring gear member  524 , and a planet carrier assembly member  526 . The planet carrier assembly member  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 .  
         [0138]    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 intermeshing pinion gears  537 ,  538  rotatably mounted on a carrier member  539  and disposed in meshing relationship with the ring gear member  534  and the sun gear member  532 , respectively.  
         [0139]    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 .  
         [0140]    The planetary gear set  550  includes a sun gear member  552 , a ring gear member  554 , and a planet carrier assembly member  556 . The planet carrier assembly member  556  includes a plurality of pinion gears  557  rotatably mounted on a carrier member  559  and disposed in meshing relationship with both the sun gear member  552  and the ring gear member  554 .  
         [0141]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  520 ,  530 ,  540  and  550  are divided into first and second transmission subsets  560 ,  561  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  560  includes planetary gear sets  520  and  530 , and transmission subset  561  includes planetary gear sets  540  and  550 . The output shaft  19  is continuously connected with members of both subsets  560  and  561 .  
         [0142]    As mentioned above, the first and second input clutches  562 ,  563  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  560  or transmission subset  561 . The first and second input clutches  562 ,  563  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  560 ,  561  prior to engaging the respective input clutches  562 ,  563 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  564 ,  565 ,  566 ,  567 ,  568 ,  569 ,  570  and  571 . The torque transmitting mechanisms  564 ,  565 ,  568  and  569  comprise braking synchronizers, and the torque transmitting mechanisms  566 ,  567 ,  570  and  571  comprise rotating synchronizers.  
         [0143]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  560 ,  561  (i.e. through the clutch  562  to the sun gear member  522  and through the clutch  563  to the sun gear member  542 ). The ring gear member  524  is continuously connected with the sun gear member  532  through the interconnecting member  572 . The ring gear member  534  is continuously connected with the planet carrier assembly member  546 , the ring gear member  554  and the output shaft  19  through the interconnecting member  574 .  
         [0144]    The sun gear member  522  is selectively connectable with the input shaft  17  through the input clutch  562 . The sun gear member  542  is selectively connectable with the input shaft  17  through the input clutch  563 . The ring gear member  524  is selectively connectable with the transmission housing  580  through the braking synchronizer  564 . The planet carrier assembly member  536  is selectively connectable with the transmission housing  580  through the braking synchronizer  565 . The planet carrier assembly member  526  is selectively connectable with the planet carrier assembly member  536  through the synchronizer  566 . The sun gear member  522  is selectively connectable with the planet carrier assembly member  536  through the synchronizer  567 . The planet carrier assembly member  556  is selectively connectable with the transmission housing  580  through the braking synchronizer  568 . The sun gear member  552  is selectively connectable with the transmission housing  580  through the braking synchronizer  569 . The ring gear member  544  is selectively connectable with the planet carrier assembly member  556  through the synchronizer  570 . The ring gear member  544  is selectively connectable with the sun gear member  552  through the synchronizer  571 .  
         [0145]    As shown in FIG. 6 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio. 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.  
         [0146]    Those skilled in the art, upon reviewing the truth table and the schematic representation of FIG. 6 a  can determine that the numerical values of the reverse and second forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  520 ,  530 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  540 ,  550 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  540 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  530 . The numerical value of the sixth forward speed ratio is  1 .  
         [0147]    The sample speed ratios given in the truth table are determined utilizing the tooth ratio values also given in FIG. 6 b . R1/S1 value is the tooth ratio of the planetary gear set  520 ; the R2/S2 value is the tooth ratio of the planetary gear set  530 ; the R3/S3 value is the tooth ratio of the planetary gear set  540 ; and the R4/S4 value is the tooth ratio of the planetary gear set  550 .  
         [0148]    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 four planetary gear sets  620 ,  630 ,  640  and  650 .  
         [0149]    The planetary gear set  620  includes a sun gear member  622 , a ring gear member  624 , and a planet carrier assembly member  626 . The planet carrier assembly member  626  includes a plurality of intermeshing pinion gears  627 ,  628  rotatably mounted on a carrier member  629  and disposed in meshing relationship with the ring gear member  624  and the sun gear member  622 , respectively.  
         [0150]    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 .  
         [0151]    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 .  
         [0152]    The planetary gear set  650  includes a sun gear member  652 , a ring gear member  654 , and a planet carrier assembly member  656 . The planet carrier assembly member  656  includes a plurality of pinion gears  657  rotatably mounted on a carrier member  659  and disposed in meshing relationship with both the sun gear member  652  and the ring gear member  654 .  
         [0153]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  620 ,  630 ,  640  and  650  are divided into first and second transmission subsets  660 ,  661  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  660  includes planetary gear sets  620  and  630 , and transmission subset  661  includes planetary gear sets  640  and  650 . The output shaft  19  is continuously connected with members of both subsets  660  and  661 .  
         [0154]    As mentioned above, the first and second input clutches  662 ,  663  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  660  or transmission subset  661 . The first and second input clutches  662 ,  663  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  660 ,  661  prior to engaging the respective input clutches  662 ,  663 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  664 ,  665 ,  666 ,  667 ,  668 ,  669 ,  670  and  671 . The torque transmitting mechanisms  664 ,  665 ,  668  and  669  comprise braking synchronizers, and the torque transmitting mechanisms  666 ,  667 ,  670  and  671  comprise rotating synchronizers.  
         [0155]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  660 ,  661  (i.e. through the clutch  662  to the sun gear member  632  and through the clutch  663  to the sun gear member  642 ). The sun gear member  622  is continuously connected with the planet carrier assembly member  636  through the interconnecting member  672 . The ring gear member  624  is continuously connected with the planet carrier assembly member  646 , the ring gear member  654  and the output shaft  19  through the interconnecting member  674 .  
         [0156]    The sun gear member  632  is selectively connectable with the input shaft  17  through the input clutch  662 . The sun gear member  642  is selectively connectable with the input shaft  17  through the input clutch  663 . The sun gear member  622  is selectively connectable with the transmission housing  680  through the braking synchronizer  664 . The planet carrier assembly member  626  is selectively connectable with the transmission housing  680  through the braking synchronizer  665 . The planet carrier assembly member  626  is selectively connectable with the ring gear member  634  through the synchronizer  666 . The ring gear member  634  is selectively connectable with the sun gear member  632  through the synchronizer  667 . The planet carrier assembly member  656  is selectively connectable with the transmission housing  680  through the braking synchronizer  668 . The sun gear member  652  is selectively connectable with the transmission housing  680  through the braking synchronizer  669 . The ring gear member  644  is selectively connectable with the planet carrier assembly member  656  through the synchronizer  670 . The ring gear member  644  is selectively connectable with the sun gear member  652  through the synchronizer  671 .  
         [0157]    As shown in FIG. 7 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio. The ratio values given are by way example and are established utilizing the ring gear/sun gear tooth ratios given in FIG. 7 b . For example, the R1/S2 value is the tooth ratio of the planetary gear set  620 ; the R2/S2 value is the tooth ratio of the planetary gear set  630 ; the R3/S3 value is the tooth ratio of the planetary gear set  640 ; and the R4/S4 value is the tooth ratio of the planetary gear set  650 . The ratio steps between adjacent forward ratios and the reverse to first ratio are also given in FIG. 7 b.    
         [0158]    Those skilled in the art will, upon reviewing the truth table of FIG. 7 b , recognize that the numerical values of the reverse and second forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  620 ,  630 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  640 ,  650 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  640 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  620 . The numerical value of the sixth forward speed ratio is 1.  
         [0159]    A powertrain  710 , shown in FIG. 8 a , has the conventional engine  12 , a planetary transmission  714 , and the conventional final drive mechanism  16 . The engine  12  is continuously connected with 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 , a third planetary gear set  740 , and a fourth planetary gear set  750 .  
         [0160]    The planetary gear set  720  includes a sun gear member  722 , a ring gear member  724 , and a planet carrier assembly member  726 . The planet carrier assembly member  726  includes a plurality of intermeshing pinion gears  727 ,  728  rotatably mounted on a carrier member  729  and disposed in meshing relationship with the ring gear member  724  and the sun gear member  722 , respectively.  
         [0161]    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 .  
         [0162]    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 .  
         [0163]    The planetary gear set  750  includes a sun gear member  752 , a ring gear member  754 , and a planet carrier assembly member  756 . The planet carrier assembly member  756  includes a plurality of intermeshing pinion gears  757 ,  758  rotatably mounted on a carrier member  759  and disposed in meshing relationship with the ring gear member  754  and the sun gear member  752 , respectively.  
         [0164]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  720 ,  730 ,  740  and  750  are divided into first and second transmission subsets  760 ,  761  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  760  includes planetary gear sets  720  and  730 , and transmission subset  761  includes planetary gear sets  740  and  750 . The output shaft  19  is continuously connected with members of both subsets  760  and  761 .  
         [0165]    As mentioned above, the first and second input clutches  762 ,  763  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  760  or transmission subset  761 . The first and second input clutches  762 ,  763  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  760 ,  761  prior to engaging the respective input clutches  762 ,  763 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  764 ,  765 ,  766 ,  767 ,  768 ,  769 ,  770  and  771 . The torque transmitting mechanisms  764 ,  765 ,  768  and  769  comprise braking synchronizers, and the torque transmitting mechanisms  766 ,  767 ,  770  and  771  comprise rotating synchronizers.  
         [0166]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  760 ,  761  (i.e. through the clutch  762  to the sun gear member  722  and through the clutch  763  to the sun gear member  742 ). The planet carrier assembly member  726  is continuously connected with the sun gear member  732  through the interconnecting member  772 . The ring gear member  734  is continuously connected with the planet carrier assembly member  746 , the ring gear member  754  and the output shaft  19  through the interconnecting member  774 .  
         [0167]    The sun gear member  722  is selectively connectable with the input shaft  17  through the input clutch  762 . The sun gear member  742  is selectively connectable with the input shaft  17  through the input clutch  763 . The ring gear member  724  is selectively connectable with the transmission housing  780  through the braking synchronizer  764 . The planet carrier assembly member  736  is selectively connectable with the transmission housing  780  through the braking synchronizer  765 . The sun gear member  722  is selectively connectable with the planet carrier assembly member  736  through the synchronizer  766 . The planet carrier assembly member  726  is selectively connectable with the sun gear member  722  through the synchronizer  767 . The planet carrier assembly member  756  is selectively connectable with the transmission housing  780  through the braking synchronizer  768 . The sun gear member  752  is selectively connectable with the transmission housing  780  through the braking synchronizer  769 . The ring gear member  744  is selectively connectable with the planet carrier assembly member  756  through the synchronizer  770 . The ring gear member  744  is selectively connectable with the sun gear member  752  through the synchronizer  771 .  
         [0168]    As shown in FIG. 8 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio. 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 R1/S1 value is the tooth ratio of the planetary gear set  720 ; the R2/S2 value is the tooth ratio of the planetary gear set  730 ; the R3/S3 value is the tooth ratio of the planetary gear set  740 ; and the R4/S4 value is the tooth ratio of the planetary gear set  750 .  
         [0169]    [0169]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 1.78.  
         [0170]    Those skilled in the art will recognize that the numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  730 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  720 ,  730 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  740 . The numerical value of the third forward speed ratio is 1. The numerical values of the fourth and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  740 ,  750 .  
         [0171]    A powertrain  810 , shown in FIG. 9 a , has the conventional engine  12 , a planetary transmission  814 , and the final drive mechanism  16 . The engine  12  is continuously connected with the input shaft  17 . The planetary transmission  814  is drivingly connected with final drive mechanism  16  through 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 , a third planetary gear set  840 , and fourth planetary gear set  850 .  
         [0172]    The planetary gear set  820  includes a sun gear member  822 , a ring gear member  824 , and a planet carrier assembly member  826 . The planet carrier assembly member  826  includes a plurality of intermeshing pinion gears  827 ,  828  rotatably mounted on a carrier member  829  and disposed in meshing relationship with the ring gear member  824  and the sun gear member  822 , respectively.  
         [0173]    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 intermeshing pinion gears  837 ,  838  rotatably mounted on a carrier member  839  and disposed in meshing relationship with the ring gear member  834  and the sun gear member  832 , respectively.  
         [0174]    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 sun gear member  842  and the ring gear member  844 .  
         [0175]    The planetary gear set  850  includes a sun gear member  852 , a ring gear member  854 , and a planet carrier assembly member  856 . The planet carrier assembly member  856  includes a plurality of pinion gears  857  rotatably mounted on a carrier member  859  and disposed in meshing relationship with both the sun gear member  852  and the ring gear member  854 .  
         [0176]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  820 ,  830 ,  840  and  850  are divided into first and second transmission subsets  860 ,  861  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  860  includes planetary gear sets  820  and  830 , and transmission subset  861  includes planetary gear sets  840  and  850 . The output shaft  19  is continuously connected with members of both subsets  860  and  861 .  
         [0177]    As mentioned above, the first and second input clutches  862 ,  863  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  860  or transmission subset  861 . The first and second input clutches  862 ,  863  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratio selection is preselected within the transmission subsets  860 ,  861  prior to engaging the respective input clutches  862 ,  863 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  864 ,  865 ,  866 ,  867 ,  868 ,  869 ,  870  and  871 . The torque transmitting mechanisms  864 ,  865 ,  868  and  869  comprise braking synchronizers, and the torque transmitting mechanisms  866 ,  867 ,  870  and  871  comprise rotating synchronizers.  
         [0178]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  860 ,  861  (i.e. through the clutch  862  to the sun gear member  822  and through the clutch  863  to the sun gear member  842 ). The planet carrier assembly member  826  is continuously connected with the sun gear member  832  through the interconnecting member  872 . The ring gear member  834  is continuously connected with the planet carrier assembly member  846 , the ring gear member  854  and the output shaft  19  through the interconnecting member  874 .  
         [0179]    The sun gear member  822  is selectively connectable with the input shaft  17  through the input clutch  862 . The sun gear member  842  is selectively connectable with the input shaft  17  through the input clutch  863 . The planet carrier assembly member  826  is selectively connectable with the transmission housing  880  through the braking synchronizer  864 . The planet carrier assembly member  836  is selectively connectable with the transmission housing  880  through the braking synchronizer  865 . The ring gear member  824  is selectively connectable with the planet carrier assembly member  836  through the synchronizer  866 . The sun gear member  822  is selectively connectable with the planet carrier assembly member  836  through the synchronizer  867 . The planet carrier assembly member  856  is selectively connectable with the transmission housing  880  through the braking synchronizer  868 . The sun gear member  852  is selectively connectable with the transmission housing  880  through the braking synchronizer  869 . The ring gear member  844  is selectively connectable with the planet carrier assembly member  856  through the synchronizer  870 . The ring gear member  844  is selectively connectable with the sun gear member  852  through the synchronizer  871 .  
         [0180]    As shown in FIG. 9 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide six forward speed ratios and a reverse speed ratio. 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 R1/S1 value is the tooth ratio of the planetary gear set  820 ; the R2/S2 value is the tooth ratio of planetary gear set  830 ; the R3/S3 value is the tooth ratio of the planetary gear set  840 ; and the R4/S4 value is the tooth ratio of the planetary gear set  850 . FIG. 9 b  also describes 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 1.60.  
         [0181]    Those skilled in the art of planetary transmissions will recognize that the numerical values of the reverse and second forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  820 ,  830 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  840 ,  850 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  840 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  830 . The numerical value of the sixth forward speed ratio is  1 .  
         [0182]    Referring to FIG. 10 a , a powertrain  910  is shown having a conventional engine  12 , a planetary transmission  914 , and a conventional final drive mechanism  16 . The planetary transmission  914  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  918 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  918  includes four planetary gear sets  920 ,  930 ,  940  and  950 .  
         [0183]    The planetary gear set  920  includes a sun gear member  922 , a ring gear member  924 , and a planet carrier assembly member  926 . The planet carrier assembly member  926  includes a plurality of pinion gears  927  rotatably mounted on a carrier member  929  and disposed in meshing relationship with both the sun gear member  922  and the ring gear member  924 .  
         [0184]    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 intermeshing pinion gears  937 ,  938  rotatably mounted on a carrier member  939  and disposed in meshing relationship with the ring gear member  934  and the sun gear member  932 , respectively.  
         [0185]    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 .  
         [0186]    The planetary gear set  950  includes a sun gear member  952 , a ring gear member  954 , and a planet carrier assembly member  956 . The planet carrier assembly member  956  includes a plurality of pinion gears  957  rotatably mounted on a carrier member  959  and disposed in meshing relationship with both the sun gear member  952  and the ring gear member  954 .  
         [0187]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  920 ,  930 ,  940  and  950  are divided into first and second transmission subsets  960 ,  961  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  960  includes planetary gear sets  920  and  930 , and transmission subset  961  includes planetary gear sets  940  and  950 . The output shaft  19  is continuously connected with members of both subsets  960  and  961 .  
         [0188]    As mentioned above, the first and second input clutches  962 ,  963  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  960  or transmission subset  961 . The first and second input clutches  962 ,  963  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  960 ,  961  prior to engaging the respective input clutches  962 ,  963 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  964 ,  965 ,  966 ,  967 ,  968 ,  969 ,  970  and  971 . The torque transmitting mechanisms  964 ,  965 ,  968  and  969  comprise braking synchronizers, and the torque transmitting mechanisms  966 ,  967 ,  970  and  971  comprise rotating synchronizers.  
         [0189]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  960 ,  961  (i.e. through the clutch  962  to the sun gear member  922  and through the clutch  963  to the sun gear member  942 ). The ring gear member  924  is continuously connected with the sun gear member  932  through the interconnecting member  972 . The ring gear member  934  is continuously connected with the planet carrier assembly member  946 , the ring gear member  954  and the output shaft  19  through the interconnecting member  974 .  
         [0190]    The sun gear member  922  is selectively connectable with the input shaft  17  through the input clutch  962 . The sun gear member  942  is selectively connectable with the input shaft  17  through the input clutch  963 . The ring gear member  924  is selectively connectable with the transmission housing  980  through the braking synchronizer  964 . The planet carrier assembly member  926  is selectively connectable with the transmission housing  980  through the braking synchronizer  965 . The planet carrier assembly member  926  is selectively connectable with the planet carrier assembly member  936  through the synchronizer  966 . The sun gear member  922  is selectively connectable with the planet carrier assembly member  936  through the synchronizer  967 . The planet carrier assembly member  956  is selectively connectable with the transmission housing  980  through the braking synchronizer  968 . The sun gear member  952  is selectively connectable with the transmission housing  980  through the braking synchronizer  969 . The ring gear member  944  is selectively connectable with the planet carrier assembly member  956  through the synchronizer  970 . The ring gear member  944  is selectively connectable with the sun gear member  952  through the synchronizer  971 .  
         [0191]    As shown in FIG. 10 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide seven forward speed ratios and a reverse speed ratio. The truth table also provides a set of examples for the numerical values 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 R1/S1 value is the tooth ratio of the planetary gear set  920 ; the R2/S2 value is the tooth ratio of the planetary gear set  930 ; the R3/S3 value is the tooth ratio of the planetary gear set  940 ; and the R4/S4 value is the tooth ratio of the planetary gear set  950 .  
         [0192]    Those skilled in the art, upon reviewing the engagement combinations, will recognize that the numerical values of the reverse, first and third forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  920 ,  930 . The numerical values of the second and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  940 ,  950 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  940 . The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  930 . The numerical value of the seventh forward speed ratio is 1.  
         [0193]    Referring to FIG. 11 a , a powertrain  1010  is shown having a conventional engine  12 , a planetary transmission  1014 , and a conventional final drive mechanism  16 . The planetary transmission  1014  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  1018 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  1018  includes four planetary gear sets  1020 ,  1030 ,  1040  and  1050 .  
         [0194]    The planetary gear set  1020  includes a sun gear member  1022 , a ring gear member  1024 , and a planet carrier assembly member  1026 . The planet carrier assembly member  1026  includes a plurality of pinion gears  1027  rotatably mounted on a carrier member  1029  and disposed in meshing relationship with both the sun gear member  1022  and the ring gear member  1024 .  
         [0195]    The planetary gear set  1030  includes a sun gear member  1032 , a ring gear member  1034 , and a planet carrier assembly member  1036 . The planet carrier assembly member  1036  includes a plurality of intermeshing pinion gears  1037 ,  1038  rotatably mounted on a carrier member  1039  and disposed in meshing relationship with the ring gear member  1034  and the sun gear member  1032 , respectively.  
         [0196]    The planetary gear set  1040  includes a sun gear member  1042 , a ring gear member  1044 , and a planet carrier assembly member  1046 . The planet carrier assembly member  1046  includes a plurality of pinion gears  1047  rotatably mounted on a carrier member  1049  and disposed in meshing relationship with both the sun gear member  1042  and the ring gear member  1044 .  
         [0197]    The planetary gear set  1050  includes a sun gear member  1052 , a ring gear member  1054 , and a planet carrier assembly member  1056 . The planet carrier assembly member  1056  includes a plurality of intermeshing pinion gears  1057 ,  1058  rotatably mounted on a carrier member  1059  and disposed in meshing relationship with the ring gear member  1054  and the sun gear member  1052 , respectively.  
         [0198]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  1020 ,  1030 ,  1040  and  1050  are divided into first and second transmission subsets  1060 ,  1061  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  1060  includes planetary gear sets  1020  and  1030 , and transmission subset  1061  includes planetary gear sets  1040  and  1050 . The output shaft  19  is continuously connected with members of both subsets  1060  and  1061 .  
         [0199]    As mentioned above, the first and second input clutches  1062 ,  1063  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  1060  or transmission subset  1061 . The first and second input clutches  1062 ,  1063  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  1060 ,  1061  prior to engaging the respective input clutches  1062 ,  1063 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  1064 ,  1065 ,  1066 ,  1067 ,  1068 ,  1069 ,  1070  and  1071 . The torque transmitting mechanisms  1064 ,  1065 ,  1068  and  1069  comprise braking synchronizers, and the torque transmitting mechanisms  1066 ,  1067 ,  1070  and  1071  comprise rotating synchronizers.  
         [0200]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  1060 ,  1061  (i.e. through the clutch  1062  to the sun gear member  1022  and through the clutch  1063  to the sun gear member  1042 ). The ring gear member  1024  is continuously connected with the sun gear member  1032  through the interconnecting member  1072 . The planet carrier assembly member  1046  is continuously connected with the ring gear member  1034 , the sun gear member  1052  and the output shaft  19  through the interconnecting member  1074 .  
         [0201]    The sun gear member  1022  is selectively connectable with the input shaft  17  through the input clutch  1062 . The sun gear member  1042  is selectively connectable with the input shaft  17  through the input clutch  1063 . The ring gear member  1024  is selectively connectable with the transmission housing  1080  through the braking synchronizer  1064 . The planet carrier assembly member  1026  is selectively connectable with the transmission housing  1080  through the braking synchronizer  1065 . The planet carrier assembly member  1026  is selectively connectable with the planet carrier assembly member  1036  through the synchronizer  1066 . The sun gear member  1022  is selectively connectable with the planet carrier assembly member  1036  through the synchronizer  1067 . The ring gear member  1054  is selectively connectable with the transmission housing  1080  through the braking synchronizer  1068 . The planet carrier assembly member  1056  is selectively connectable with the transmission housing  1080  through the braking synchronizer  1069 . The ring gear member  1044  is selectively connectable with the ring gear member  1054  through the synchronizer  1070 . The ring gear member  1044  is selectively connectable with the planet carrier assembly member  1056  through the synchronizer  1071 .  
         [0202]    As shown in FIG. 11 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide seven forward speed ratios and a reverse speed ratio. The truth table also provides a set of examples for the numerical values 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. 11 b . The R1/S1 value is the tooth ratio of the planetary gear set  1020 ; the R2/S2 value is the tooth ratio of the planetary gear set  1030 ; the R3/S3 value is the tooth ratio of the planetary gear set  1040 ; and the R4/S4 value is the tooth ratio of the planetary gear set  1050 .  
         [0203]    Those skilled in the art, upon reviewing the engagement combinations, will recognize that the numerical values of the reverse, first and third forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear set  1020 ,  1030 . The numerical values of the second and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear set  1040 ,  1050 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1040 . The numerical value of the fifth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1030 . The numerical value of the seventh forward speed ratio is 1.  
         [0204]    Referring to FIG. 12 a , a powertrain  1110  is shown having a conventional engine  12 , a planetary transmission  1114 , and a conventional final drive mechanism  16 . The planetary transmission  1114  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  1118 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  1118  includes four planetary gear sets  1120 ,  1130 ,  1140  and  1150 .  
         [0205]    The planetary gear set  1120  includes a sun gear member  1122 , a ring gear member  1124 , and a planet carrier assembly member  1126 . The planet carrier assembly member  1126  includes a plurality of pinion gears  1127  rotatably mounted on a carrier member  1129  and disposed in meshing relationship with both the sun gear member  1122  and the ring gear member  1124 .  
         [0206]    The planetary gear set  1130  includes a sun gear member  1132 , a ring gear member  1134 , and a planet carrier assembly member  1136 . The planet carrier assembly member  1136  includes a plurality of intermeshing pinion gears  1137 ,  1138  rotatably mounted on a carrier member  1139  and disposed in meshing relationship with the ring gear member  1134  and the sun gear member  1132 , respectively.  
         [0207]    The planetary gear set  1140  includes a sun gear member  1142 , a ring gear member  1144 , and a planet carrier assembly member  1146 . The planet carrier assembly member  1146  includes a plurality of pinion gears  1147  rotatably mounted on a carrier member  1149  and disposed in meshing relationship with both the sun gear member  1142  and the ring gear member  1144 .  
         [0208]    The planetary gear set  1150  includes a sun gear member  1152 , a ring gear member  1154 , and a planet carrier assembly member  1156 . The planet carrier assembly member  1156  includes a plurality of pinion gears  1157  rotatably mounted on a carrier member  1159  and disposed in meshing relationship with both the sun gear member  1152  and the ring gear member  1154 .  
         [0209]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  1120 ,  1130 ,  1140  and  1150  are divided into first and second transmission subsets  1160 ,  1161  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  1160  includes planetary gear sets  1120  and  1130 , and transmission subset  1161  includes planetary gear sets  1140  and  1150 . The output shaft  19  is continuously connected with members of both subsets  1160  and  1161 .  
         [0210]    As mentioned above, the first and second input clutches  1162 ,  1163  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  1160  or transmission subset  1061 . The first and second input clutches  1162 ,  1163  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  1160 ,  1161  prior to engaging the respective input clutches  1162 ,  1163 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  1164 ,  1165 ,  1166 ,  1167 ,  1168 ,  1169 ,  1170  and  1171 . The torque transmitting mechanisms  1164 ,  1165 ,  1168  and  1169  comprise braking synchronizers, and the torque transmitting mechanisms  1166 ,  1167 ,  1170  and  1171  comprise rotating synchronizers.  
         [0211]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  1160 ,  1161  (i.e. through the clutch  1162  to the sun gear member  1122  and through the clutch  1163  to the sun gear member  1142 ). The planet carrier assembly member  1126  is continuously connected with the sun gear member  1132  through the interconnecting member  1172 . The planet carrier assembly member  1146  is continuously connected with the ring gear member  1134 , the ring gear member  1154  and the output shaft  19  through the interconnecting member  1174 .  
         [0212]    The sun gear member  1122  is selectively connectable with the input shaft  17  through the input clutch  1162 . The sun gear member  1142  is selectively connectable with the input shaft  17  through the input clutch  1163 . The planet carrier assembly member  1126  is selectively connectable with the transmission housing  1180  through the braking synchronizer  1164 . The ring gear member  1124  is selectively connectable with the transmission housing  1180  through the braking synchronizer  1165 . The sun gear member  1122  is selectively connectable with the planet carrier assembly member  1136  through the synchronizer  1166 . The ring gear member  1124  is selectively connectable with the planet carrier assembly member  1136  through the synchronizer  1167 . The planet carrier assembly member  1156  is selectively connectable with the transmission housing  1180  through the braking synchronizer  1168 . The sun gear member  1152  is selectively connectable with the transmission housing  1180  through the braking synchronizer  1169 . The ring gear member  1144  is selectively connectable with the planet carrier assembly member  1156  through the synchronizer  1170 . The ring gear member  1144  is selectively connectable with the sun gear member  1152  through the synchronizer  1171 .  
         [0213]    As shown in FIG. 12 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide seven forward speed ratios and a reverse speed ratio. The truth table also provides a set of examples for the numerical values 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. 12 b . The R1/S1 value is the tooth ratio of the planetary gear set  1120 ; the R2/S2 value is the tooth ratio of the planetary gear set  1130 ; the R3/S3 value is the tooth ratio of the planetary gear set  1140 ; and the R4/S4 value is the tooth ratio of the planetary gear set  1150 .  
         [0214]    Those skilled in the art, upon reviewing the engagement combinations, will recognize that the numerical values of the reverse, second and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  1120 ,  1130 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  1140 ,  1150 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1140 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1130 . The numerical value of the seventh forward speed ratio is 1.  
         [0215]    Referring to FIG. 13 a , a powertrain  1210  is shown having a conventional engine  12 , a planetary transmission  1214 , and a conventional final drive mechanism  16 . The planetary transmission  1214  includes an input shaft  17  connected with the engine  12 , a planetary gear arrangement  1218 , and an output shaft  19  continuously connected with the final drive mechanism  16 . The planetary gear arrangement  1218  includes four planetary gear sets  1220 ,  1230 ,  1240  and  1250 .  
         [0216]    (The planetary gear set  1220  includes a sun gear member  1222 , a ring gear member  1224 , and a planet carrier assembly member  1226 . The planet carrier assembly member  1226  includes a plurality of pinion gears  1227  rotatably mounted on a carrier member  1229  and disposed in meshing relationship with both the sun gear member  1222  and the ring gear member  1224 .  
         [0217]    The planetary gear set  1230  includes a sun gear member  1232 , a ring gear member  1234 , and a planet carrier assembly member  1236 . The planet carrier assembly member  1236  includes a plurality of intermeshing pinion gears  1237 ,  1238  rotatably mounted on a carrier member  1239  and disposed in meshing relationship with the ring gear member  1234  and the sun gear member  1232 , respectively.  
         [0218]    The planetary gear set  1240  includes a sun gear member  1242 , a ring gear member  1244 , and a planet carrier assembly member  1246 . The planet carrier assembly member  1246  includes a plurality of pinion gears  1247  rotatably mounted on a carrier member  1249  and disposed in meshing relationship with both the sun gear member  1242  and the ring gear member  1244 .  
         [0219]    The planetary gear set  1250  includes a sun gear member  1252 , a ring gear member  1254 , and a planet carrier assembly member  1256 . The planet carrier assembly member  1256  includes a plurality of intermeshing pinion gears  1257 ,  1258  rotatably mounted on a carrier member  1259  and disposed in meshing relationship with the ring gear member  1254  and the sun gear member  1252 , respectively.  
         [0220]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  1220 ,  1230 ,  1240  and  1250  are divided into first and second transmission subsets  1260 ,  1261  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  1260  includes planetary gear sets  1220  and  1230 , and transmission subset  1261  includes planetary gear sets  1240  and  1250 . The output shaft  19  is continuously connected with members of both subsets  1260  and  1261 .  
         [0221]    As mentioned above, the first and second input clutches  1262 ,  1263  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  1260  or transmission subset  1261 . The first and second input clutches  1262 ,  1263  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  1260 ,  1261  prior to engaging the respective input clutches  1262 ,  1263 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes eight torque transmitting mechanisms  1264 ,  1265 ,  1266 ,  1267 ,  1268 ,  1269 ,  1270  and  1271 . The torque transmitting mechanisms  1264 ,  1265 ,  1268  and  1269  comprise braking synchronizers, and the torque transmitting mechanisms  1266 ,  1267 ,  1270  and  1271  comprise rotating synchronizers.  
         [0222]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  1260 ,  1261  (i.e. through the clutch  1262  to the sun gear member  1222  and through the clutch  1263  to the sun gear member  1242 ). The planet carrier assembly member  1226  is continuously connected with the sun gear member  1232  through the interconnecting member  1272 . The planet carrier assembly member  1246  is continuously connected with the ring gear member  1234 , the sun gear member  1252 , and the output shaft  19  through the interconnecting member  1274 .  
         [0223]    The sun gear member  1222  is selectively connectable with the input shaft  17  through the input clutch  1262 . The sun gear member  1242  is selectively connectable with the input shaft  17  through the input clutch  1263 . The planet carrier assembly member  1226  is selectively connectable with the transmission housing  1280  through the braking synchronizer  1264 . The ring gear member  1224  is selectively connectable with the transmission housing  1280  through the braking synchronizer  1265 . The sun gear member  1222  is selectively connectable with the planet carrier assembly member  1236  through the synchronizer  1266 . The ring gear member  1224  is selectively connectable with the planet carrier assembly member  1236  through the synchronizer  1267 . The ring gear member  1254  is selectively connectable with the transmission housing  1280  through the braking synchronizer  1268 . The planet carrier assembly member  1256  is selectively connectable with the transmission housing  1280  through the braking synchronizer  1269 . The ring gear member  1244  is selectively connectable with the ring gear member  1254  through the synchronizer  1270 . The ring gear member  1244  is selectively connectable with the planet carrier assembly member  1256  through the synchronizer  1271 .  
         [0224]    As shown in FIG. 13 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide seven forward speed ratios and a reverse speed ratio. The truth table also provides a set of examples for the numerical values 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. 13 b . The R1/S1 value is the tooth ratio of the planetary gear set  1220 ; the R2/S2 value is the tooth ratio of the planetary gear set  1230 ; the R3/S3 value is the tooth ratio of the planetary gear set  1240 ; and the R4/S4 value is the tooth ratio of the planetary gear set  1250 .  
         [0225]    Those skilled in the art, upon reviewing the engagement combinations, will recognize that the numerical values of the reverse, second and sixth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  1220 ,  1230 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  1240 ,  1250 . The numerical value of the third forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1240 . The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1230 . The numerical value of the seventh forward speed ratio is  1 .  
         [0226]    [0226]FIGS. 14 a  and  14   b  illustrate a transmission wherein one of the torque transmitting mechanisms from a previously described configuration is eliminated to realize five forward speed ratios and a reverse speed ratio. Specifically, the powertrain  1310 , shown in FIG. 14 a  is identical to that shown in FIG. 5 a , except that the synchronizer  471  of FIG. 5 a  has been eliminated.  
         [0227]    The powertrain  1310 , shown in FIG. 14 a , includes the conventional engine  12 , a planetary transmission  1314 , and the conventional final drive mechanism  16 . The engine  12  is selectively connectable with the planetary transmission  1314  through the input shaft  17 . The planetary transmission is drivingly connected with the final drive mechanism  16  through the input shaft  17 . The planetary transmission  1314  includes a planetary gear arrangement  1318  that has a first planetary gear set  1320 , a second planetary gear set  1330 , a third planetary gear set  1340 , and a fourth planetary gear set  1350 .  
         [0228]    The planetary gear set  1320  includes a sun gear member  1322 , a ring gear member  1324 , and a planet carrier assembly member  1326 . The planet carrier assembly member  1326  includes a plurality of pinion gears  1327  rotatably mounted on a carrier member  1329  and disposed in meshing relationship with both the sun gear member  1322  and the ring gear member  1324 .  
         [0229]    The planetary gear set  1330  includes a sun gear member  1332 , a ring gear member  1334 , and a planet carrier assembly member  1336 . The planet carrier assembly member  1336  includes a plurality of pinion gears  1337  rotatably mounted on a carrier member  1339  and disposed in meshing relationship with both the sun gear member  1332  and the ring gear member  1334 .  
         [0230]    The planetary gear set  1340  includes a sun gear member  1342 , a ring gear member  1344 , and a planet carrier assembly member  1346 . The planet carrier assembly member  1346  includes a plurality of pinion gears  1347  rotatably mounted on a carrier member  1349  and disposed in meshing relationship with both the sun gear member  1342  and the ring gear member  1344 .  
         [0231]    The planetary gear set  1350  includes a sun gear member  1352 , a ring gear member  1354 , and a planet carrier assembly member  1356 . The planet carrier assembly member  1356  includes a plurality of intermeshing pinion gears  1357 ,  1358  rotatably mounted on a carrier member  1359  and disposed in meshing relationship with the ring gear member  1354  and the sun gear member  1352 , respectively.  
         [0232]    As a result of the dual clutch arrangement of the invention, the four planetary gear sets  1320 ,  1330 ,  1340  and  1350  are divided into first and second transmission subsets  1360 ,  1361  which are alternatively engaged to provide odd number and even number speed ranges, respectively. Transmission subset  1360  includes planetary gear sets  1320  and  1330 , and transmission subset  1361  includes planetary gear sets  1340  and  1350 . The output shaft  19  is continuously connected with members of both subsets  1360  and  1361 .  
         [0233]    As mentioned above, the first and second input clutches  1362 ,  1363  are alternatively engaged for transmitting power from the input shaft  17  to transmission subset  1360  or transmission subset  1361 . The first and second input clutches  1362 ,  1363  are controlled electronically, and the disengaged input clutch is gradually engaged while the engaged input clutch is gradually disengaged to facilitate transfer of power from one transmission subset to another. In this manner, shift quality is maintained, as in an automatic transmission, while providing better fuel economy because no torque converter is required, and hydraulics associated with “wet” clutching are eliminated. All speed ratios are preselected within the transmission subsets  1360 ,  1361  prior to engaging the respective input clutches  1362 ,  1363 . The preselection is achieved by means of electronically controlled synchronizers. As shown, the planetary gear arrangement includes seven torque transmitting mechanisms  1364 ,  1365 ,  1366 ,  1367 ,  1368 ,  1369  and  1370 . The torque transmitting mechanism  1364 ,  1365 ,  1368  and  1369  comprise braking synchronizers, and the torque transmitting mechanisms  1366 ,  1367  and  1370  comprise rotating synchronizers.  
         [0234]    Accordingly, the input shaft  17  is alternately connected with the first and second transmission subsets  1360 ,  1361  (i.e. through the clutch  1362  to the sun gear member  1322  and through the clutch  1363  to the sun gear member  1342 ). The ring gear member  1324  is continuously connected with the sun gear member  1332  through the interconnecting member  1372 . The planet carrier assembly member  1346  is continuously connected with the ring gear members  1334 ,  1354  and the output shaft  19  through the interconnecting member  1374 .  
         [0235]    The sun gear member  1322  is selectively connectable with the input shaft  17  through the input clutch  1362 . The sun gear member  1342  is selectively connectable with the input shaft  17  through the input clutch  1363 . The planet carrier assembly member  1326  is selectively connectable with the transmission housing  1380  through the braking synchronizer  1364 . The planet carrier assembly member  1336  is selectively connectable with the transmission housing  1380  through the braking synchronizer  1365 . The sun gear member  1322  is selectively connectable with the planet carrier assembly member  1336  through the synchronizer  1366 . The planet carrier assembly member  1326  is selectively connectable with the sun gear member  1322  through the synchronizer  1367 . The planet carrier assembly member  1356  is selectively connectable with the transmission housing  1380  through the braking synchronizer  1368 . The sun gear member  1352  is selectively connectable with the transmission housing  1380  through the braking synchronizer  1369 . The ring gear member  1344  is selectively connectable with the planet carrier assembly member  1356  through the synchronizer  1370 .  
         [0236]    As shown in FIG. 13 b , and in particular the truth table disclosed therein, the input clutches and torque transmitting mechanisms are selectively engaged in combinations of three to provide five forward speed ratios and a reverse speed ratio. A sample of the numerical values for the ratios is also provided in the truth table of the FIG. 13 b . These values are determined utilizing the ring gear/sun gear tooth ratios also given in Figure  13   b . The R1/S1 value is the tooth ratio of the planetary gear set  1320 ; the R2/S2 value is the tooth ratio of the planetary gear set  1330 ; the R3/S3 value is the tooth ratio of the planetary gear set  1340 ; and the R4/S4 value is the tooth ratio of the planetary gear set  1350 . Also given in FIG. 13 b  is a chart describing the step ratios between the adjacent forward speed ratios and the reverse to first forward speed ratio.  
         [0237]    Those skilled in the art will recognize that the numerical value of the reverse speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1330 . The numerical values of the first and fifth forward speed ratios are determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  1320 ,  1330 . The numerical value of the second forward speed ratio is determined utilizing the ring gear/sun gear tooth ratio of the planetary gear set  1340 . The numerical value of the third forward speed ratio is 1. The numerical value of the fourth forward speed ratio is determined utilizing the ring gear/sun gear tooth ratios of the planetary gear sets  1340 ,  1350 .  
         [0238]    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