Patent Publication Number: US-9423005-B2

Title: Multi-speed transmission

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 13/569,462 filed Aug. 8, 2012, the disclosure of which is incorporated in its entirety by reference herein. This application is also a continuation-in-part of U.S. application Ser. No. 13/771,660 filed Feb. 20, 2013, the disclosure of which is incorporated in its entirety by reference herein. 
    
    
     TECHNICAL FIELD 
     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 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a first transmission gearing arrangement. 
         FIG. 2  is a schematic diagram of a second transmission gearing arrangement. 
         FIG. 3  is a schematic diagram of a third transmission gearing arrangement. 
         FIG. 4  is a schematic diagram of a fourth transmission gearing arrangement. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     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 and an output. 
     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. 
       FIGS. 1 and 2  depict a transaxle that provides a variety of speed ratios between input  50  and output  52 . Input  50  may be driven by an internal combustion engine or other prime mover. A launch device such as torque converter or launch clutch may be employed between the prime mover and transaxle input  50  permitting the engine to idle while the vehicle is stationary and a transaxle ratio is selected. Output  52  may be a sprocket driving a chain that transmits power to a differential axis. Alternatively, output  52  may be a gear that transmits power to a differential axis through a series of meshes. In a longitudal arrangement, input  50  would enter from the left and output  52  would be a shaft extending to the right. 
     The transaxle of  FIGS. 1 and 2  utilizes four simple planetary gear sets  10 ,  20 ,  30 , and  40 . A planet carrier  12  rotates about a central axis and supports a set of planet gears  14  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  16  and with internal gear teeth on a ring gear  18 . The sun gear and ring gear are supported to rotate about the same axis as the carrier. Gear sets  20 ,  30 , and  40  are similarly structured. Gear set  30  may be positioned beside the other gear sets. However, to reduce axial length, gear set  30  may be positioned radially outside gear sets  10  and  20  as shown in  FIG. 1  or radially outside gear set  40  as shown in  FIG. 2 . 
     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. 
     A suggested ratio of gear teeth for each planetary gear set is listed in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 Ring 18/Sun 16 
                 2.00 
               
               
                   
                 Ring 28/Sun 26 
                 1.80 
               
               
                   
                 Ring 38/Sun 36 
                 1.50 
               
               
                   
                 Ring 48/Sun 46 
                 2.00 
               
               
                   
                   
               
            
           
         
       
     
     Sun gear  36  is fixedly held against rotation; carrier  42  is fixedly coupled to input  50 ; carrier  12  is fixedly coupled to ring gear  28 ; and ring gear  18 , carrier  22 , ring gear  38 , and sun gear  46  are mutually fixedly coupled. Output  52  is selectively coupled to carrier  32  by clutch  60  and selectively coupled to ring gear  48  by clutch  62 . Input  50  is selectively coupled to sun gear  26  by clutch  64 . Sun gear  16  is selectively coupled to input  50  by clutch  66  and selectively held against rotation by brake  68 . The combination of carrier  12  and ring gear  28  is selectively held against rotation by brake  70 . Optional one-way-brake  72  passively precludes the combination of carrier  12  and ring gear  28  from rotating in a negative direction while permitting rotation in the positive direction. 
     Various combinations of gear sets, clutches, and brakes selectively impose particular speed relationships. The combination of gear sets  10  and  20  impose a linear speed relationship among sun gear  16 , the combination of carrier  12  and ring gear  28 , the combination of ring  18  and carrier  22 , and sun gear  26 . The combination of gear set  30  and clutch  60  selectively imposes an underdrive relationship between carrier  22  and output  52 . In other words, when clutch  60  is engaged, output  52  is constrained to rotate slower than carrier  22  and in the same direction. 
     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  50  and output  52 . An X indicates that the shift element is required to establish the speed ratio. An (X) indicates the clutch can be applied but is not required. In 4th gear, clutches  60  and  62  establish the power flow path between input  50  and output  52 . Any one of the remaining shift elements can also be applied. Applying clutch  64  ensures that all single and two step shifts from 4th gear can be accomplished by engaging only one shift element and releasing only one shift element. When the gear sets have tooth numbers as indicated in Table 1, the speed ratios have the values indicated in Table 2. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 60 
                 62 
                 64 
                 66 
                 68 
                 70 
                 Ratio 
                 Step 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Rev 
                 X 
                   
                   
                 X 
                   
                 X 
                 −3.33 
                 71% 
               
               
                 1 st   
                 X 
                   
                 X 
                   
                   
                 X 
                 4.67 
               
               
                 2 nd   
                 X 
                   
                 X 
                   
                 X 
                   
                 2.67 
                 1.75 
               
               
                 3 rd   
                 X 
                   
                 X 
                 X 
                   
                   
                 1.67 
                 1.60 
               
               
                 4 th   
                 X 
                 X 
                 (X) 
                   
                   
                   
                 1.22 
                 1.36 
               
               
                 5 th   
                   
                 X 
                 X 
                 X 
                   
                   
                 1.00 
                 1.22 
               
               
                 6 th   
                   
                 X 
                 X 
                   
                 X 
                   
                 0.84 
                 1.19 
               
               
                 7 th   
                   
                 X 
                 X 
                   
                   
                 X 
                 0.76 
                 1.11 
               
               
                 8 th   
                   
                 X 
                   
                   
                 X 
                 X 
                 0.67 
                 1.14 
               
               
                 9 th   
                   
                 X 
                   
                 X 
                   
                 X 
                 0.57 
                 1.17 
               
               
                   
               
            
           
         
       
     
     A second example transaxle is illustrated in  FIGS. 3 and 4 . This transaxle utilizes three simple planetary gear sets  10 ,  20 , and  40 , each having a sun gear, a ring gear, and a planet carrier supported for rotation about a first axis. Additionally, axis transfer gears  82  and  86  are supported for rotation about this first axis. Gear  86  is radially larger than gear  82 . Output gear  52  and axis transfer gears  84  and  88  are supported for rotation about a second axis substantially parallel to the first axis. Output  52  transmits power to a differential axis through an additional gear mesh. Gear  84  meshes with gear  82  and gear  88  meshes with gear  86 . Carrier  42  is fixedly coupled to input  50 ; axis transfer gear  84  is fixedly coupled to output gear  52 ; carrier  12  is fixedly coupled to ring gear  28 ; and ring gear  18 , carrier  22 , and sun gear  46  are mutually fixedly coupled. Axis transfer gear  82  is selectively coupled to carrier  22  by clutch  60 ′. Output gear  52  is selectively coupled to axis transfer gear  88  by clutch  62 ′. Input  50  is selectively coupled to sun gear  26  by clutch  64 . Sun gear  16  is selectively coupled to input  50  by clutch  66  and selectively held against rotation by brake  68 . The combination of carrier  12  and ring gear  28  is selectively held against rotation by brake  70 . Optional one-way-brake  72  passively precludes the combination of carrier  12  and ring gear  28  from rotating in a negative direction while permitting rotation in the positive direction. 
     To save axial space, gear  86  may be located radially outside of ring gear  48  as shown in  FIG. 3 . Alternatively, planetary gear set  40  may be located radially outside of planetary gear sets  10  and  20  as shown in  FIG. 4 . 
     Various combinations of gear sets, clutches, and brakes selectively impose particular speed relationships. The combination of gear sets  10  and  20  impose a linear speed relationship among sun gear  16 , the combination of carrier  12  and ring gear  28 , the combination of ring  18  and carrier  22 , and sun gear  26 . The combination of axis transfer gear  82 , axis transfer gear  84 , and clutch  60 ′ selectively imposes a first speed ratio between carrier  22  and output  52 . In other words, when clutch  60 ′ is engaged, the speed of output  52  divided by the speed of carrier  22  is a first fixed value, which is a negative value. Similarly, the combination of axis transfer gear  86 , axis transfer gear  88 , and clutch  62 ′ selectively imposes a second speed ratio between ring gear  48  and output  52 . When clutch  62 ′ is engaged, the speed of output  52  divided by the speed of ring gear  48  is a second fixed value. The second fixed value is also negative value but is greater in absolute value than the first fixed value. 
     A suggested ratio of gear teeth for each planetary gear set and each pair of axis transfer gears is listed in Table 3. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
             
            
               
                   
                 Ring 18/Sun 16 
                 1.88 
               
               
                   
                 Ring 28/Sun 26 
                 1.65 
               
               
                   
                 Ring 48/Sun 46 
                 2.00 
               
               
                   
                 Gear 84/Gear 82 
                 1.68 
               
               
                   
                 Gear 88/Gear 86 
                 1.06 
               
               
                   
                   
               
            
           
         
       
     
     As shown in Table 4, engaging the shift elements in combinations of three establishes nine forward speed ratios and one reverse speed ratio between input  50  and output  52 . When the gear sets have tooth numbers as indicated in Table 3, the speed ratios have the values indicated in Table 4. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 60′ 
                 62′ 
                 64 
                 66 
                 68 
                 70 
                 Ratio 
                 Step 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Rev 
                 X 
                   
                   
                 X 
                   
                 X 
                 −3.14 
                 71% 
               
               
                 1 st   
                 X 
                   
                 X 
                   
                   
                 X 
                 4.44 
               
               
                 2 nd   
                 X 
                   
                 X 
                   
                 X 
                   
                 2.64 
                 1.68 
               
               
                 3 rd   
                 X 
                   
                 X 
                 X 
                   
                   
                 1.67 
                 1.57 
               
               
                 4 th   
                 X 
                 X 
                 (X) 
                   
                   
                   
                 1.26 
                 1.32 
               
               
                 5 th   
                   
                 X 
                 X 
                 X 
                   
                   
                 1.06 
                 1.19 
               
               
                 6 th   
                   
                 X 
                 X 
                   
                 X 
                   
                 0.90 
                 1.18 
               
               
                 7 th   
                   
                 X 
                 X 
                   
                   
                 X 
                 0.81 
                 1.11 
               
               
                 8 th   
                   
                 X 
                   
                   
                 X 
                 X 
                 0.71 
                 1.14 
               
               
                 9 th   
                   
                 X 
                   
                 X 
                   
                 X 
                 0.60 
                 1.18 
               
               
                   
               
            
           
         
       
     
     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.