Abstract:
A transmission gearing arrangement produces nine forward speed ratios and one reverse speed ratio by selective engagement of three shift elements in various combinations. Some embodiment includes four simple planetary gear sets and six shift elements of which one is a brake. Another embodiment includes two axis transfer gear pairs in place of one of the planetary gear sets.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to the field of automatic transmissions for motor vehicles. More particularly, the disclosure pertains to an arrangement of gears, clutches, and the interconnections among them in a power transmission. 
       BACKGROUND 
       [0002]    Many vehicles are used over a wide range of vehicle speeds, including both forward and reverse movement. Some types of engines, however, are capable of operating efficiently only within a narrow range of speeds. Consequently, transmissions capable of efficiently transmitting power at a variety of speed ratios are frequently employed. When the vehicle is at low speed, the transmission is usually operated at a high speed ratio such that it multiplies the engine torque for improved acceleration. At high vehicle speed, operating the transmission at a low speed ratio permits an engine speed associated with quiet, fuel efficient cruising. Typically, a transmission has a housing mounted to the vehicle structure, an input shaft driven by an engine crankshaft, and an output shaft driving the vehicle wheels, often via a differential assembly which permits the left and right wheel to rotate at slightly different speeds as the vehicle turns. 
       SUMMARY OF THE DISCLOSURE 
       [0003]    In a first embodiment, a transmission includes first, second, and third gearing arrangements. The first gearing arrangement fixedly constrains a first shaft to rotate faster than an input shaft and in a same direction. The first gearing arrangement may be, for example, a simple planetary gear set. Alternatively, the first gearing arrangement may be, as another example, a collection of axis transfer gears in combination with a clutch. The second gearing arrangement selectively imposes a linear speed relationship between a second shaft, the input shaft, and an output shaft. The second gearing arrangement may be, for example, a simple planetary gear set in combination with a clutch. The third gearing arrangement fixedly imposes a linear speed relationship between a third shaft, the output shaft, and a fourth shaft. The third gearing arrangement may be, for example, a simple planetary gear set. The transmission may further comprise a brake and second, third, and fourth clutches. The transmission may additionally comprise a fourth gearing arrangement, which may be a simple planetary gear set in combination with a clutch. 
         [0004]    In a second embodiment, a transmission includes a gearing arrangement and first, second, and third simple planetary gear sets, first, second, and third clutches, and a brake. The gearing arrangement fixedly constrains a first shaft to rotate faster than an input shaft and in a same direction. The first gearing arrangement may be, for example, a fourth simple planetary gear set. Alternatively, the gearing arrangement may be, as another example, a collection of axis transfer gears in combination with a clutch. The first simple planetary gear set selectively imposes a linear speed relationship between the first shaft, a second shaft, and the third shaft. The second simple planetary gear set selectively imposes a linear speed relationship between the second shaft, the input shaft, and an output shaft. The third simple planetary gear set fixedly imposes a linear speed relationship between a third shaft, the output shaft, and a fourth shaft. The transmission may further include fourth and fifth clutches. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a schematic diagram of a first transmission gearing arrangement. 
           [0006]      FIG. 2  is a schematic diagram of a second transmission gearing arrangement. 
           [0007]      FIG. 3  is a schematic diagram of a third transmission gearing arrangement. 
           [0008]      FIG. 4  is a schematic diagram of a fourth transmission gearing arrangement. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
         [0010]    A gearing arrangement is a collection of rotating elements and shift elements configured to impose specified speed relationships among the rotating elements. Some speed relationships, called fixed speed relationships, are imposed regardless of the state of any shift elements. Other speed relationships, called selective speed relationships, are imposed only when particular shift elements are fully engaged. A linear speed relationship exists among an ordered list of rotating elements when i) the first and last rotating element in the group are constrained to have the most extreme speeds, ii) the speeds of the remaining rotating elements are each constrained to be a weighted average of the first and last rotating element, and iii) when the speeds of the rotating elements differ, they are constrained to be in the listed order, either increasing or decreasing. The speed of an element is positive when the element rotates in one direction and negative when the element rotates in the opposite direction. A discrete ratio transmission has a gearing arrangement that selectively imposes a variety of speed ratios between an input shaft and an output shaft. 
         [0011]    A group of rotating elements are fixedly coupled to one another if they are constrained to rotate as a unit in all operating conditions. Rotating elements can be fixedly coupled by spline connections, welding, press fitting, machining from a common solid, or other means. Slight variations in rotational displacement between fixedly coupled elements can occur such as displacement due to lash or shaft compliance. One or more rotating elements that are all fixedly coupled to one another may be called a shaft. In contrast, two rotating elements are selectively coupled by a shift element when the shift element constrains them to rotate as a unit whenever it is fully engaged and they are free to rotate at distinct speeds in at least some other operating condition. A shift element that holds a rotating element against rotation by selectively connecting it to the housing is called a brake. A shift element that selectively couples two or more rotating elements to one another is called a clutch. Shift elements may be actively controlled devices such as hydraulically or electrically actuated clutches or brakes or may be passive devices such as one way clutches or brakes. Two rotating elements are coupled if they are either fixedly coupled or selectively coupled. 
         [0012]    An example transmission is schematically illustrated in  FIG. 1 . The transmission utilizes four simple planetary gear sets  20 ,  30 ,  40 , and  50 . A planet carrier  32  rotates about a central axis and supports a set of planet gears  34  such that the planet gears rotate with respect to the planet carrier. External gear teeth on the planet gears mesh with external gear teeth on a sun gear  36  and with internal gear teeth on a ring gear  38 . The sun gear and ring gear are supported to rotate about the same axis as the carrier. Gear sets  20 ,  40 , and  50  are similarly structured. 
         [0013]    A simple planetary gear set is a type of gearing arrangement that imposes a fixed linear speed relationship among the sun gear, the planet carrier, and the ring gear. Other known types of gearing arrangements also impose a fixed linear speed relationship among three rotating elements. For example, a double pinion planetary gear set imposes a fixed linear speed relationship between the sun gear, the ring gear, and the planet carrier. 
         [0014]    A suggested ratio of gear teeth for each planetary gear set is listed in Table 1. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 Ring 28/Sun 26 
                 1.729 
               
               
                   
                 Ring 38/Sun 36 
                 1.624 
               
               
                   
                 Ring 48/Sun 46 
                 2.274 
               
               
                   
                 Ring 58/Sun 56 
                 3.430 
               
               
                   
                   
               
             
          
         
       
     
         [0015]    In the transmission of  FIG. 1 , input shaft  10  is fixedly coupled to carrier  22  and carrier  42  and selectively coupled to intermediate shaft  74  by clutch  68 . Intermediate shaft  74  is fixedly coupled to ring gear  38  and sun gear  56 . Output shaft  12  is fixedly coupled to carrier  52  and ring gear  48 . Sun gear  26  is fixedly held against rotation. Sun gear  36  is selectively coupled to ring gear  28  by clutch  60 . Carrier  32  is selectively coupled to ring gear  28  by clutch  62 , to ring gear  58  by clutch  64 , and to sun gear  46  by clutch  66 . Ring gear  58  is selectively held against rotation by brake  70 . 
         [0016]    Various combinations of gear sets, clutches, and brakes selectively impose particular speed relationships. Gear set  20  fixedly imposes an overdrive relationship between carrier  22  and ring gear  28 . In other words, ring gear  28  is constrained to rotate faster than carrier  22  and in the same direction in all operating conditions. The combination of gear set  40  and clutch  66  selectively imposes various speed relationships between carrier  32 , input shaft  10 , and output shaft  12 . Engaging clutch  66  couples sun gear  46  to carrier  32  and imposes a linear speed relationship between carrier  32 , input shaft  10 , and output shaft  12 . Gear set  50  fixedly imposes a linear speed relationship between sun gear  56 , output shaft  12 , and ring gear  58 . The combination of gear set  30  and clutches  60 ,  62 ,  64 , and  66  selectively imposes various speed relationships between ring gear  28 , carrier  32 , and sun gear  56 . Engaging clutch  60  couples sun gear  36  to ring gear  28  and, in combination with engaging at least one of clutches  62 ,  64 , and  66 , imposes a linear speed relationship between ring gear  28 , carrier  32 , and sun gear  56 . 
         [0017]    As shown in Table 2, engaging the shift elements in combinations of three establishes nine forward speed ratios and one reverse speed ratio between input shaft  10  and output shaft  12 . An X indicates that the shift element is required to establish the speed ratio. When the gear sets have tooth number ratios as indicated in Table 1, the speed ratios have the values indicated in Table 2. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 60 
                 62 
                 64 
                 66 
                 68 
                 70 
                 Ratio 
                 Step 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Rev. 
                 X 
                   
                 X 
                   
                   
                 X 
                 −4.558 
                 103% 
               
               
                 1 st   
                 X 
                   
                   
                   
                 X 
                 X 
                 4.430 
               
               
                 2 nd   
                 X 
                 X 
                   
                   
                   
                 X 
                 2.807 
                 1.58 
               
               
                 3 rd   
                 X 
                   
                   
                 X 
                   
                 X 
                 1.877 
                 1.50 
               
               
                 4 th   
                 X 
                 X 
                   
                 X 
                   
                   
                 1.341 
                 1.40 
               
               
                 5 th   
                 X 
                   
                   
                 X 
                 X 
                   
                 1.107 
                 1.21 
               
               
                 6 th   
                   
                   
                 X 
                 X 
                 X 
                   
                 1.000 
                 1.11 
               
               
                 7 th   
                 X 
                   
                 X 
                   
                 X 
                   
                 0.854 
                 1.17 
               
               
                 8 th   
                   
                 X 
                 X 
                   
                 X 
                   
                 0.691 
                 1.24 
               
               
                 9 th   
                 X 
                 X 
                 X 
                   
                   
                   
                 0.634 
                 1.09 
               
               
                   
               
             
          
         
       
     
         [0018]    When the driver selects drive (forward), the transmission is prepared for vehicle launch in 1st by engaging clutches  60  and  68  and brake  70 . A shift to 2nd may be accomplished by gradually disengaging clutch  68  while gradually engaging clutch  62 . Additional upshifts are accomplished according to Table 2. When the driver selects reverse, the transmission is prepared for vehicle launch in reverse by engaging clutches  60  and  64  and brake  70 . 
         [0019]    A second example transmission is illustrated in  FIG. 2 . This transmission utilizes four simple planetary gear sets with suggested tooth number ratios as shown in Table 1. In this transmission, input shaft  10  is fixedly coupled to carrier  22  and carrier  42  and selectively coupled to intermediate shaft  74  by clutch  68 . Intermediate shaft  74  is fixedly coupled to sun gear  56  and selectively coupled to ring gear  38  by clutch  60 ′. Output shaft  12  is fixedly coupled to carrier  52  and ring gear  48 . Sun gear  26  is fixedly held against rotation. Sun gear  36  is fixedly coupled to ring gear  28 . Carrier  32  is selectively coupled to ring gear  28  by clutch  62 , to ring gear  58  by clutch  64 , and to sun gear  46  by clutch  66 . Ring gear  58  is selectively held against rotation by brake  70 . The transmission of  FIG. 2  is operated in the same fashion as the transmission of  FIG. 1 . 
         [0020]    Various combinations of gear sets, clutches, and brakes selectively impose particular speed relationships. Gear set  20  fixedly imposes an overdrive relationship between carrier  22  and ring gear  28 . In other words, ring gear  28  is constrained to rotate faster than carrier  22  and in the same direction in all operating conditions. The combination of gear set  40  and clutch  66  selectively imposes various speed relationships between carrier  32 , input shaft  10 , and output shaft  12 . Engaging clutch  66  couples sun gear  46  to carrier  32  and imposes a linear speed relationship between carrier  32 , input shaft  10 , and output shaft  12 . Gear set  50  fixedly imposes a linear speed relationship between sun gear  56 , output shaft  12 , and ring gear  58 . The combination of gear set  30  and clutches  60 ′,  62 ,  64 , and  66  selectively imposes various speed relationships between ring gear  28 , carrier  32 , and sun gear  56 . Engaging clutch  60 ′ couples ring gear  38  to intermediate shaft  74  and, in combination with engaging at least one of clutches  62 ,  64 , and  66 , imposes a linear speed relationship between ring gear  28 , carrier  32 , and sun gear  56 . 
         [0021]    A third example transmission is illustrated in  FIG. 3 . This transmission utilizes four simple planetary gear sets with suggested tooth number ratios as shown in Table 1. In this transmission, input shaft  10  is fixedly coupled to carrier  22  and carrier  42  and selectively coupled to intermediate shaft  74  by clutch  68 . Intermediate shaft  74  is fixedly coupled to ring gear  38  and sun gear  56 . Output shaft  12  is fixedly coupled to carrier  52  and selectively coupled to ring gear  48  by clutch  66 ′. Sun gear  26  is fixedly held against rotation. Sun gear  36  is selectively coupled to ring gear  28  by clutch  60 . Carrier  32  is fixedly coupled to sun gear  46  and selectively coupled to ring gear  28  by clutch  62  and to ring gear  58  by clutch  64 . Ring gear  58  is selectively held against rotation by brake  70 . The transmission of  FIG. 3  is operated in the same fashion as the transmissions of  FIGS. 1 and 2 . 
         [0022]    Various combinations of gear sets, clutches, and brakes selectively impose particular speed relationships. Gear set  20  fixedly imposes an overdrive relationship between carrier  22  and ring gear  28 . In other words, ring gear  28  is constrained to rotate faster than carrier  22  and in the same direction in all operating conditions. The combination of gear set  40  and clutch  66 ′ selectively imposes various speed relationships between carrier  32 , input shaft  10 , and output shaft  12 . Engaging clutch  66 ′ couples ring gear  48  to the output shaft and imposes a linear speed relationship between carrier  32 , input shaft  10 , and output shaft  12 . Gear set  50  fixedly imposes a linear speed relationship between sun gear  56 , output shaft  12 , and ring gear  58 . The combination of gear set  30  and clutches  60 ,  62 ,  64 , and  66 ′ selectively imposes various speed relationships between ring gear  28 , carrier  32 , and sun gear  56 . Engaging clutch  60  couples sun gear  36  to ring gear  28  and, in combination with engaging at least one of clutches  62 ,  64 , and  66 ′, imposes a linear speed relationship between ring gear  28 , carrier  32 , and sun gear  56 . 
         [0023]    A fourth example transmission is illustrated in  FIG. 4 . This transmission utilizes three simple planetary gear sets  30 ,  40 , and  50  with suggested tooth number ratios as indicated in Table 1. These simple planetary gear sets have a sun gear, a ring gear, and a carrier that rotate about a central axis. Additionally, axis transfer gears  82  and  88  are supported for rotation about this central axis. Gear  82  is radially larger than gear  88 . Layshaft  72  is parallel to the central axis but offset from the central axis. Axis transfer gears  84  and  86  are supported for rotation about the axis of layshaft  72 . Axis transfer gears  84  and  86  continuously mesh with axis transfer gears  82  and  88  respectively. 
         [0024]    Input shaft  10  is fixedly coupled to axis transfer gear  82  and carrier  42  and selectively coupled to intermediate shaft  74  by clutch  68 . Intermediate shaft  74  is fixedly coupled to ring gear  38  and sun gear  56 . Intermediate shaft  76  is fixedly coupled to axis transfer gear  88 . Output shaft  12  is fixedly coupled to carrier  52  and ring gear  48 . Sun gear  36  is selectively coupled to intermediate shaft  76  by clutch  60 . Carrier  32  is selectively coupled to intermediate shaft  76  by clutch  62 , to ring gear  58  by clutch  64 , and to sun gear  46  by clutch  66 . Ring gear  58  is selectively held against rotation by brake  70 . This arrangement may be suitable for front wheel drive transmissions in which an axis transfer from the engine axis to the differential axis is required. The transmission of  FIG. 5  is operated in the same fashion as the transmissions of  FIGS. 1-4 . 
         [0025]    The combination of axis transfer gears  82 ,  84 ,  86 , and  88  impose an overdrive relationship between input shaft  10  and intermediate shaft  76 . In other words, intermediate shaft  76  is constrained to rotate faster than input shaft  10  and in the same direction. The combination of gear set  40  and clutch  66  selectively imposes various speed relationships between carrier  32 , input shaft  10 , and output shaft  12 . Engaging clutch  66  couples sun gear  46  to carrier  32  and imposes a linear speed relationship between carrier  32 , input shaft  10 , and output shaft  12 . Gear set  50  fixedly imposes a linear speed relationship between sun gear  56 , output shaft  12 , and ring gear  58 . Ring gear  58  may be selectively held against rotation by engaging or disengaging brake  70 . Sun gear  56  may be selectively constrained to rotate at the same speed as input shaft  10  and in the same direction by engaging or disengaging clutch  68 . The combination of gear set  30  and clutches  60 ,  62 ,  64 , and  66  selectively imposes various speed relationships between intermediate shaft  76 , carrier  32 , and sun gear  56 . Engaging clutch  60  couples sun gear  36  to intermediate shaft  76  and, in combination with engaging at least one of clutches  62 ,  64 , and  66 , imposes a linear speed relationship between ring gear  28 , carrier  32 , and sun gear  56 . 
         [0026]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.