Abstract:
A power transmission includes an input; an output; a first gearset including an output having a lower speed than a speed of the input; a second gearset having first, second, and third rotating elements; a second gearset having fourth, fifth, sixth, and seventh rotating elements; four clutches; and two brakes. The brakes and clutches are engaged in combinations of three to produce up to eleven forward speed ratios and two reverse speed ratios.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the field of automatic transmissions for motor vehicles. More particularly, the invention pertains to a kinematic arrangement of gearing, clutches, brakes, and the interconnections among them in a power transmission. 
     SUMMARY OF THE INVENTION 
     A power transmission includes an input, output, a gearset including an output having a lower speed than a speed of the input, second sun gear, second ring gear driveably connected to the output of the gearset, second carrier, second pinions supported on the second carrier and meshing with the second sun gear and the second ring gear, a third sun gear, a fourth sun gear, a third ring gear driveably connected to the output, a third carrier, third pinions supported on the third carrier and meshing with the third sun gear and the third ring gear, and fourth pinions meshing with the fourth sun gear and the third pinions. 
     The transmission provides ten forward gears or speed ratios (nine forward gears and a special purpose low gear), and two reverse gears. There is also an alternative forward gear ratio that can be selected, making a total of eleven forward ratios. The gearsets are controlled by six control elements—four clutches and two brakes. Three of the control elements are engaged and three are disengaged in order to produce each of the forward and reverse gears. 
     The transmission is applicable to front wheel drive and rear wheel drive vehicles. 
     The scope of applicability of the preferred embodiment will become apparent from the following detailed description, claims and drawings. It should be understood, that the description and specific examples, although indicating preferred embodiments of the invention, are given by way of illustration only. Various changes and modifications to the described embodiments and examples will become apparent to those skilled in the art. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be more readily understood by reference to the following description, taken with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram showing a kinematic arrangement of a multi-speed transmission; 
         FIG. 2  is a table showing a preferred number of teeth for the gears and pinions of the transmission of  FIG. 1 ; 
         FIG. 3  is a table indicating the states of the clutches and brakes corresponding to the forward and reverse speed ratios of the transmission of  FIG. 1  when the gears have the number of teeth indicated in  FIG. 2 ; 
         FIG. 4  is a schematic diagram of a front planetary gearset of a second embodiment; 
         FIG. 5  is a schematic diagram showing a kinematic arrangement of a multi-speed transmission; 
         FIG. 6  is a table showing a preferred number of teeth for the gears and pinions of the transmission of  FIG. 5 ; and 
         FIG. 7  is a table indicating the states of the clutches and brakes corresponding to forward and reverse speed ratios of the transmission of  FIG. 5 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A transmission  8  according to a first embodiment is illustrated schematically in  FIG. 1 . Input shaft  10  is driven by a vehicle engine, preferably through a torque converter. Output shaft  12  drives the vehicle wheels, preferably through a differential. 
     A simple, planetary, epicyclic, speed reduction gearset  20  includes a sun gear  22  having external gear teeth that are continually held against rotation, a ring gear  24  having internal gear teeth and secured to input shaft  10 , a planet carrier  26 , and a set of planet pinions  28  supported for rotation on carrier  26  and meshing with both sun gear  22  and ring gear  24 . If the speed of input shaft  10  is 1.00, the speed of carrier  26  is about 0.6875 provided the gears and pinions have the number of teeth shown in  FIG. 2 . Carrier  26  and ring gear  34  comprise a second input. 
     A second simple, planetary, epicyclic gearset  30  includes a sun gear  32  having external gear teeth, a ring gear  34  having internal gear teeth, a planet carrier  36 , and a set of planet pinions  38  supported for rotation on carrier  36  and meshing with both sun gear  32  and ring gear  34 . Brake  66  selectively holds sun gear  32  against rotation. If the speed of ring gear  34  is 0.6875, the speed of carrier  36  is about 0.4727 provided brake  66  is applied and the gears and pinions have the number of teeth shown in  FIG. 2 . 
     A Ravigneaux epicyclic gearset  40  includes a sun gear  42  having external gear teeth, a sun gear  44  having external gear teeth, a ring gear  46  having internal gear teeth, a planet carrier  48 , a set of planet pinions  50  supported for rotation on carrier  48  and meshing with sun gear  42  and ring gear  46 , and a set of planet pinions  52  supported for rotation on carrier  48  and meshing with sun gear  44  and pinions  50 . 
     Ring gear  24  is connected directly to the input shaft  10 . Carrier  26  is connected directly to ring gear  34 . Sun gear  22  is held fixed against rotation on the transmission casing  54 . Ring gear  46  is connected directly to the transmission output shaft  12 . 
     Four rotating clutches, preferably multi-plate friction clutches, connect rotating elements to one another such that they rotate as a unit when hydraulic pressure is applied to a hydraulic servo that controls the clutch. Clutch  56  selectively connects carrier  36  to sun gear  44 . Clutch  58  selectively connects carrier  36  to sun gear  42 . Clutch  60  selectively connects sun gear  32  and brake  66  to a sun gear  42 . Clutch  64  selectively connects carrier  48  to input shaft  10 . 
     Brake  62  selectively holds carrier  48  against rotation. A one-way brake  68  arranged in parallel with brake  62  between the transmission casing  54  and carrier  48  allows for non-synchronous gear shifts between low gear and 2 nd  gear and between 1 st  gear and 2 nd  gear. 
     Brake  66  selectively holds sun gear  32  against rotation. 
     Suggested tooth numbers for the gears and pinions are shown in  FIG. 2 . 
       FIG. 3  indicates the engaged and disengaged states of the clutches and brakes for each of the forward speed ratios, a reverse speed ratio, an alternate reverse speed ratio, and an alternate fifth gear. 
     To launch the vehicle from rest in 1st gear, hydraulic pressure is applied to engage clutch  56 , brake  62  and brake  66  while all other brakes and clutches are disengaged. 
     To shift from 1st gear to 2nd gear, brake  62  is disengaged while clutch  60  is engaged, while maintaining clutch  56  and brake  66  engaged and all other brakes and clutches disengaged. 
     To shift from 2nd gear to 3rd gear, clutch  60  is disengaged while clutch  58  is engaged, while maintaining clutch  56  and brake  66  engaged and all other brakes and clutches disengaged. 
     To shift from 3rd gear to 4th gear, brake  66  is disengaged while clutch  60  is engaged while maintaining clutch  56  and clutch  58  engaged and all other brakes and clutches disengaged. 
     To shift from 4th gear to 5th gear, clutch  58  is disengaged while clutch  64  is engaged, while maintaining clutch  56  and clutch  60  engaged and all other brakes and clutches disengaged. 
     To shift from 5th gear to 6th gear, clutch  60  is disengaged while clutch  58  is engaged while maintaining clutch  56  and clutch  64  engaged and all other brakes and clutches disengaged. Clutch  56  remains engaged while operating in 1st through 6th gears. 
     To shift from 6th gear to 7th gear, clutch  56  is disengaged while clutch  60  is engaged while maintaining clutch  58  and clutch  64  engaged and all other brakes and clutches disengaged. 
     To shift from 7th gear to 8th gear, clutch  60  is disengaged while brake  66  is engaged while maintaining clutch  58  and clutch  64  engaged and all other brakes and clutches disengaged. 
     To shift from 8th gear to 9th gear, clutch  58  is disengaged, clutch  60  is engaged while maintaining clutch  64  and brake  66  engaged and all other brakes and clutches disengaged. Clutch  64  remains engaged while operating in 5th through 9th gears. 
     To shift from 3rd gear to the alternate 5th gear, clutch  58  is disengaged, clutch  64  is engaged, clutch  56  and brake  66  remain engaged, and all other brakes and clutches disengaged. 
     To shift from the alternate 5th gear to 6th gear, brake  66  is disengaged while clutch  58  is engaged, clutch  56  and clutch  64  remain engaged and all other brakes and clutches disengaged. 
     A special low ratio is also available which may be used for special purposes such as off road usage, high altitude usage, carrying or towing heavy loads, or to enable elimination of a torque converter. This special low ratio is selected by applying clutch  56 , clutch  60  and brake  62  while disengaging all other brakes and clutches. 
     Reverse gear is selected by applying clutch  58 , brake  62  and brake  66 , while disengaging all other brakes and clutches. An alternate reverse gear is selected by applying clutch  58 , clutch  60  and brake  62 , while disengaging all other brakes and clutches. 
       FIG. 4  is a schematic diagram of a second embodiment, wherein the axial positions of gearsets  20  and  30  are reversed with respect to their locations in  FIG. 1 . As described above, gearset  20  includes sun gear  22  fixed against rotation; a ring gear  24 , secured to input shaft  10 ; a planet carrier  26 ; and a set of planet pinions  28  supported for rotation on carrier  26  and meshing with both sun gear  22  and ring gear  24 . The second gearset  30  includes a sun gear  32 , connected to brake  66  and clutch  60 ; a ring gear  34 , secured to carrier  26 ; a planet carrier  36 , connected to clutches  56  and  58 ; and a set of planet pinions  38  supported for rotation on carrier  36  and meshing with both sun gear  32  and ring gear  34 . 
     A transmission  80  is illustrated schematically in  FIG. 5 . A first input  82  is driven by a vehicle engine, preferably through a torque converter. Output  84  drives the vehicle wheels, preferably through a differential. 
     An epicyclic speed reduction gearset  86  includes a sun gear  88  continually held against rotation, a ring gear  90  secured to input  82 , a planet carrier  92 , and a set of planet pinions  94  supported for rotation on carrier  92  and meshing with both sun gear  88  and ring gear  90 . If the speed of input  82  is 1.00, the speed of carrier  92  is about 0.706 provided the gears and pinions have the number of teeth shown in  FIG. 6 . 
     A second epicyclic gearset  96  includes a sun gear  98 , a ring gear  100  secured to carrier  92 , a planet carrier  102 , and a set of planet pinions  104  supported for rotation on carrier  102  and meshing with both sun gear  98  and ring gear  100 . Brake  106  selectively holds sun gear  98  against rotation. Except for operation in eighth gear, the speed of carrier  102  is less than the speed of input  82  in each of the forward and reverse gears. In eighth gear, the speed of carrier  102  is 1.00 provided the state of the brakes and clutches are as shown in  FIG. 7 , the gears and pinions have the number of teeth shown in  FIG. 6 , and the speed of input  82  is 1.00. 
     A bridging Simpson epicyclic gearset  110  includes mutually connected sun gears  112 ,  114 , ring gears  116 ,  118 ,  120 , planet carriers  122 ,  124 , a set of planet pinions  126  supported for rotation on carrier  122  and meshing with sun gear  112  and ring gears  116 ,  118 , and a set of planet pinions  128  supported for rotation on carrier  124  and meshing with sun gear  114  and ring gear  120 . 
     Ring gear  116  is connected directly to the output  84 . Carrier  124  is connected directly to ring gear  118 . Sun gears  112 ,  114  are connected to clutches  130 ,  132 . Carrier  122  is selectively held fixed against rotation on the transmission casing by brake  134 . Carrier  122  is also selectively connected through clutch  136  to input  82  and ring gear  90 . Ring gear  120  is connected directly to clutch  138 . 
     The four rotating clutches  130 ,  132 ,  136 ,  138 , preferably multi-plate friction clutches, connect rotating elements to one another such that they rotate as a unit when hydraulic pressure is applied to a hydraulic servo that controls the clutch. Clutch  130  selectively connects sun gears  112 ,  114  to carrier  102 . Clutch  132  selectively connects sun gear  98  to sun gears  112 ,  114 . Clutch  136  selectively connects carrier  122  to input  82 . Clutch  138  selectively connects ring gear  120  to carrier  102 . 
     Brake  106  selectively holds sun gear  98  against rotation. Brake  134  selectively holds carrier  122  against rotation. A one-way brake, arranged in parallel with brake  134  between the transmission casing and carrier  122 , allows for non-synchronous gear shifts between low gear and 2 nd  gear and between 1 st  gear and 2 nd  gear. 
     Suggested tooth numbers for the gears and pinions are shown in  FIG. 6 . 
       FIG. 7  indicates the engaged and disengaged states of the clutches  130 ,  132 ,  136 ,  138  and brakes  106 ,  134  for each of eleven forward speed ratios, a primary reverse speed ratio, and an alternate reverse speed ratio. 
     To launch the vehicle from rest in 1st gear, hydraulic pressure is applied to engage clutch  138 , brake  134  and clutch  132  while all other brakes and clutches are disengaged. 
     To shift from 1st gear to 2nd gear, clutch  132  is disengaged, brake  106  is engaged, clutch  138  and brake  134  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 2nd gear to 3rd gear, brake  134  is disengaged, clutch  132  is engaged, clutch  138  and brake  106  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 3rd gear to 4th gear, clutch  132  is disengaged, clutch  130  is engaged, clutch  138  and brake  106  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 4th gear to 5th gear, brake  106  is disengaged, clutch  132  is engaged, clutches  138 ,  130  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 5th gear to 6th gear, clutches  130 ,  132  are disengaged, brake  106  and clutch  136  are engaged, clutch  138  remains engaged, and brake  134  is disengaged. 
     To shift from 6th gear to 7th gear, brake  106  is disengaged, clutch  132  is engaged, clutches  138 ,  136  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 7th gear to 8th gear, clutch  132  is disengaged, clutch  130  is engaged, clutches  138 ,  136  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 8th gear to 9th gear, clutch  138  is disengaged, clutch  132  is engaged, clutches  130 ,  136  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 9 th  gear to the 10th gear, clutch  132  is disengaged, brake  106  is engaged, clutches  130 ,  136  remain engaged, and all other brakes and clutches remain disengaged. 
     To shift from 10 th  gear to 11th gear, clutch  130  is disengaged, clutch  132  is engaged, brake  106  and clutch  136  remain engaged, and all other brakes and clutches remain disengaged. 
     Reverse gear is produced by applying clutch  130 , brake  106  and brake  134 , while disengaging all other brakes and clutches. An alternate reverse gear is produced by applying clutch  130 , brake  134  and clutch  132 , while disengaging all other brakes and clutches. 
     Throughout this description, two elements are connected when they are constrained to rotate at the same speed in all operating conditions. Connections may be effectuated by spline connections, welding, machining from common stock or other means and may involve intermediate parts. Slight variations in relative displacement due to effects such as shaft compliance or lash are permissible. Two elements are releasably connected by a clutch when they are constrained to rotate at the same speed whenever the clutch is engaged and are capable of rotating at different speeds in some other operating condition. 
     In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that the alternate embodiments can be practiced otherwise than as specifically illustrated and described.