Abstract:
A multiple speed power transmission comprising: an input shaft, an output shaft, a first epicyclic gearing assembly with five rotating members, a second epicyclic gearing assembly with three rotating members, two clutches, and four brakes capable of producing nine forward speed ratios and one reverse speed ratio when clutches and brakes are applied in combinations of two.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a schematic diagram of a transmission according to a first embodiment of the present invention which produces nine forward and one reverse speed ratios. 
           [0003]      FIG. 2  is a table showing proposed tooth numbers for the gears of the transmission illustrated in  FIG. 1 . 
           [0004]      FIG. 3  is a table indicating the states of the clutches and the resulting speed ratios of the transmission in  FIG. 1  when the gears have the number of teeth indicated in  FIG. 2 . 
           [0005]      FIG. 4  is a lever diagram illustrating the speed relationships of a transmission according to the present invention. 
           [0006]      FIG. 5  is a schematic diagram of a transmission according to a second embodiment of the present invention which produces nine forward and one reverse speed ratios. 
           [0007]      FIG. 6  is a table showing proposed tooth numbers for the gears of the transmission illustrated in  FIG. 5 . 
           [0008]      FIG. 7  is a table indicating the states of the clutches and the resulting speed ratios of the transmission in  FIG. 5  when the gears have the number of teeth indicated in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]    A transmission according to a first embodiment of the present invention is illustrated schematically in  FIG. 1 . Input shaft  10  is driven by the vehicle engine, preferably via a torque converter. Output shaft  12  drives the vehicle wheels, preferably via a differential. 
         [0010]    Four simple planetary gear sets  20 ,  30 ,  40 , and  50  each have a sun gear with external gear teeth, a ring gear with internal gear teeth, a planet carrier, and a set of planet gears that are supported for rotation with respect to the carrier and mesh with both the sun gear and the ring gear. Sun gears  22  and  42  are connected directly to the input shaft  10 . Ring gear  54  is connected directly to the transmission output shaft. Ring gear  24 , carrier  36 , ring gear  44 , and sun gear  52  are mutually connected such that they rotate in unison. Similarly, ring gear  34  and carrier  46  are mutually connected. Suggested tooth numbers for these gears are shown in  FIG. 2 . 
         [0011]    Four brakes  60 ,  62 ,  64 , and  66  selectively hold particular elements against rotation, providing a reaction torque. Preferably, these brakes are multi-plate friction clutches which hold the element to transmission case  14  when hydraulic pressure is applied to the clutch piston. Brake  60  selectively holds carrier  26  to transmission case  14 . Brake  62  selectively holds sun gear  32  to transmission case  14 . Brake  64  selectively holds ring gear  24 , carrier  36 , ring gear  44 , and sun gear  52  to transmission case  14 . Brake  66  selectively holds carrier  56  to transmission case  14 . Two rotating clutches connect rotating element to one another such that they are forced to rotate as a unit. These are also preferably multi-plate friction clutches. Clutch  68  selectively connects the input shaft  10  to carrier  56 . Clutch  70  selectively connects carrier  46  and ring gear  34  to carrier  56 . 
         [0012]      FIG. 3  indicates the states of the clutches for each of the nine forward ratios and the one reverse ratio. 
         [0013]    To launch the vehicle from rest in 1st gear, hydraulic pressure is applied to engage brake  66  and clutch  70  while all other brakes and clutches are disengaged. To shift from 1st gear to 2nd gear, brake  66  is gradually disengaged while brake  60  is gradually engaged. To shift from 2nd gear to 3rd gear, brake  60  is gradually disengaged while brake  64  is gradually engaged. To shift from 3rd gear to 4th gear, brake  64  is gradually disengaged while brake  62  is gradually engaged. To shift from 4th gear to 5th gear, brake  62  is gradually disengaged while clutch  68  is gradually engaged. Clutch  70  remains engaged while operating in 1st through 5th gears. To shift from 5th gear to 6th gear, clutch  70  is gradually disengaged while brake  62  is gradually engaged. To shift from 6th gear to 7th gear, brake  62  is gradually disengaged while brake  64  is gradually engaged. Finally, to shift from 7th gear to 8th gear, brake  64  is gradually disengaged while brake  60  is gradually engaged. Clutch  68  remains engaged while operating in 5th through 8th gears. 
         [0014]    A special low ratio is also available which may be used for special purposes such as off road usage or may be used to enable elimination of a torque converter. This ratio is selected by applying brake  60  and brake  66  while disengaging all other brakes and clutches. If the transmission does not include a torque converter or other dedicated launch device, the transmission is prepared for forward launch in low by engaging only brake  60 . Then, brake  66  is gradually applied based on the torque demanded by the driver. To shift from low to 1st gear, brake  60  is gradually disengaged while clutch  70  is gradually engaged, maintaining brake  66  in the engaged state. 
         [0015]    Reverse ratio is selected by applying brake  62  and brake  66  while disengaging all other brakes and clutches. If the transmission does not include a torque converter or other dedicated launch device, the transmission is prepared for reverse launch by engaging only brake  62 . Then, brake  66  is gradually applied based on driver demand. 
         [0016]      FIG. 4  is a lever diagram illustrating the speed relationships among elements of a transmission according to the present invention. Gear sets  20 ,  30 , and  40  of  FIG. 1  collectively form an epicyclic gearing assembly with five rotating bodies that each rotate about the central axis. The speeds of these five bodies are linearly related such that the speeds of any two bodies determine the speeds of the remaining three bodies. These three gear sets correspond to the left lever in  FIG. 4 . Body A corresponds to sun gear  22  and sun gear  42 . Body B corresponds to ring gear  34  and carrier  46 . Body C corresponds to carrier  26 . Body D corresponds to ring gear  24 , carrier  36 , and ring gear  44 . Body E corresponds to sun gear  32 . Gear set  50  is an epicyclic gearing assembly with three elements and corresponds to the right lever in  FIG. 4 . Body D corresponds to sun gear  52  which is connected to the elements making up body D within the left lever. Body F corresponds to carrier  56 . Body G corresponds to ring gear  54 . The speeds of these three bodies are linearly related such that the speeds of any two of them determine the speed of the remaining body. 
         [0017]    When the gear sets of  FIG. 1  have the tooth numbers indicated in  FIG. 2 , the speed of body B is equal to 0.6518 times the speed of body D plus (1−0.6518) times the speed of body A. These weighting factors impact the overall speed ratio in 1st through 5th gears. Similarly, the speed of body C is equal to 0.7456 times the speed of body D plus (1−0.7456) times the speed of body A. These weighting factors impact the ratio in low and 8th. The speed of body D is equal to 0.6054 times the speed of body E plus (1−0.6054) times the speed of body A. These weighting factors impact the reverse speed ratio. Finally, the speed of body F is equal to 0.3364 times the speed of body D plus (1−0.3364) times the speed of body G. These last weighting factors influence all of the ratios except direct drive. Many other configurations of planetary gear sets are available which produce weighting factors very close to this, including configurations that include double pinion planetary gear sets and gear sets that share planet gears. Any of these alternate configurations may be substituted and the same overall speed ratios will result. 
         [0018]    A transmission according to a second embodiment of the present invention is illustrated schematically in  FIG. 5 . This embodiment also corresponds to the stick diagram of  FIG. 4 , but uses a different configuration of planetary gear sets corresponding to the left lever. Input shaft  10  is driven by the vehicle engine, preferably via a torque converter. Output shaft  12  drives the vehicle wheels, preferably via a differential. 
         [0019]    Four simple planetary gear sets  80 ,  90 ,  100 , and  110  each have a sun gear with external gear teeth, a ring gear with internal gear teeth, a planet carrier, and a set of planet gears that are supported for rotation with respect to the carrier and mesh with both the sun gear and the ring gear. Sun gear  92  is connected directly to the input shaft  10 . Ring gear  114  is connected directly to the transmission output shaft. Ring gear  84 , carrier  96 , and carrier  96  are mutually connected. Similarly, carrier  86 , ring gear  94 , sun gear  102 , and sun gear  112  are mutually connected. Suggested tooth numbers for these gears are shown in  FIG. 6 . 
         [0020]    Four brakes  60 ,  62 ,  64 , and  66  selectively hold particular elements against rotation, providing a reaction torque. Brake  60  selectively holds ring gear  84 , carrier  96 , and carrier  106  to transmission case  14 . Brake  62  selectively holds sun gear  82  to transmission case  14 . Brake  64  selectively holds carrier  86 , ring gear  94 , sun gear  102 , and sun gear  112  to transmission case  14 . Brake  66  selectively holds carrier  116  to transmission case  14 . Two rotating clutches connect rotating element to one another such that they are forced to rotate as a unit. Clutch  68  selectively connects the input shaft  10  to carrier  116 . Clutch  70  selectively connects ring gear  104   34  to carrier  116 . 
         [0021]      FIG. 7  indicates the states of the clutches for each of the nine forward ratios and the one reverse ratio. The operation of this embodiment is identical to the operation of the embodiment of  FIGS. 1-3  as described above. 
         [0022]    The first three gear sets of  FIG. 5  contain five rotating bodies that each rotate about the central axis. The speeds of these five bodies are linearly related such that the speeds of any two bodies determine the speeds of the remaining three bodies. These three gear sets correspond to the left lever in  FIG. 4 . Body A corresponds to sun gear  92 . Body B corresponds to ring gear  104 . Body C corresponds to ring gear  84 , carrier  96 , and carrier  106 . Body D corresponds carrier  86 , ring gear  94 , and sun gear  102 . Body E corresponds to sun gear  82 . Gear set  110  corresponds to the right lever in  FIG. 4 . Body D corresponds to sun gear  112  which is connected to the elements making up body D within the left lever. Body F corresponds to carrier  116 . Body G corresponds to ring gear  114 . The speeds of these three bodies are linearly related such that the speeds of any two of them determine the speed of the remaining body. 
         [0023]    When the gear sets of  FIG. 1  have the tooth numbers indicated in  FIG. 2 , the speed of body B is equal to 0.5762 times the speed of body D plus (1−0.5762) times the speed of body A. Similarly, the speed of body C is equal to 0.6967 times the speed of body D plus (1−0.6967) times the speed of body A. The speed of body D is equal to 0.5671 times the speed of body E plus (1−0.5671) times the speed of body A. Finally, the speed of body F is equal to 0.3364 times the speed of body D plus (1−0.3364) times the speed of body G. Any alternate configuration of gearing that produce approximately these same relationships may be substituted without departing from the spirit of this invention. 
         [0024]    In accordance with the provisions of the patent statutes, the preferred embodiment has been described. However, it should be noted that alternate embodiments can be practiced otherwise than as specifically illustrated and described.