Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application is a continuation of U.S. application Ser. No. 11/689,138, filed Mar. 21, 2007 now U.S. Pat. No. 7,699,741, which claims priority to U.S. Provisional Application No. 60/879,957, filed on Jan. 25, 2007. 
    
    
     TECHNICAL FIELD 
     The invention relates to a multi-speed transmission having both a plurality of planetary gear sets and torque transmitting devices that are selectively engageable to achieve multiple gear ratios. 
     BACKGROUND 
     A typical multi-speed transmission uses a combination of friction clutches and planetary gear arrangements to achieve a plurality of gear ratios. The number and placement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios. 
     While conventional transmissions achieve their intended purpose, the need for new and improved transmission configurations continues with the design of lighter and more compact vehicles. Accordingly, there is a need for a cost-effective, compact and multi-speed transmission. 
     SUMMARY 
     A transmission is provided having an input member, an output member, a plurality of planetary gear sets, a plurality of interconnecting members and a plurality of torque-transmitting mechanisms. The plurality of planetary gear sets has first, second and third members. The input member is continuously interconnected with the second member of the second planetary gear set. The output member is continuously interconnected with the second member of the fourth planetary gear set. A first interconnecting member continuously interconnects the first member of the first planetary gear set with the first member of the second planetary gear set. A second interconnecting member continuously interconnects the second member of the first planetary gear set with the third member of the fourth planetary gear set. A third interconnecting member continuously interconnects the third member of the second planetary gear set with the first member of the third planetary gear set. A fourth interconnecting member continuously interconnects the second member of the third planetary gear set with a second member of the fourth planetary gear set. A first torque-transmitting mechanism selectively interconnects the first member of the first planetary gear set with a stationary member. A second torque-transmitting mechanism selectively interconnects the third member of the first planetary gear set with the stationary member. A third torque-transmitting mechanism selectively interconnecting the second member of the second planetary gear set with the first member of the fourth planetary gear set. A fourth torque-transmitting mechanism selectively interconnects the first member of the third planetary gear set with the first member of fourth planetary gear set. A fifth torque-transmitting mechanism selectively interconnects the third member of the third planetary gear set with the first member of the fourth planetary gear set. The torque-transmitting mechanisms are engageable in combinations of at least three to establish at least eight forward speed ratios and at least one reverse speed ratio between the input member and the output member. 
     In another aspect of the present invention, the first member is a sun gear. 
     In yet another aspect of the present invention, the second member is a carrier member. 
     In yet another aspect of the present invention, the third member is a ring gear. 
     In yet another aspect of the present invention, the input member is continuously connected to the carrier member of the second planetary gear set. 
     In yet another aspect of the present invention, the output member is continuously connected to the carrier member of the fourth planetary gear set. 
     In yet another aspect of the present invention, the third torque-transmitting mechanism selectively interconnects a carrier member of the second planetary gear set with a sun gear of the fourth planetary gear set. 
     In yet another aspect of the present invention, the third torque-transmitting mechanism selectively interconnects the input member with a sun gear of the fourth planetary gear set 
     In yet another aspect of the present invention, the fourth torque-transmitting mechanism selectively interconnects a sun gear of the third planetary gear set with a sun gear of the fourth planetary gear set. 
     In yet another aspect of the present invention, the fourth torque-transmitting mechanism selectively interconnects a sun gear of the fourth planetary gear set with a sun gear of the third planetary gear set and a ring gear of the second planetary gear set. 
     In yet another aspect of the present invention, the fifth torque-transmitting mechanism selectively interconnects a ring gear of the third planetary gear set with a sun gear of the fourth planetary gear set. 
     In yet another aspect of the present invention, the first interconnecting member continuously interconnects a sun gear of the first planetary gear set with a sun gear of the second planetary gear set. 
     In yet another aspect of the present invention, the second interconnecting member continuously interconnects a carrier member of the first planetary gear set with a ring gear of the fourth planetary gear set. 
     In yet another aspect of the present invention, the third interconnecting member continuously interconnects a ring gear of the second planetary gear set with a sun gear of the third planetary gear set. 
     In yet another aspect of the present invention, the fourth interconnecting member continuously interconnects a carrier member of the third planetary gear set with a carrier member of the fourth planetary gear set. 
     In yet another aspect of the present invention, the first torque-transmitting mechanism selectively interconnects a sun gear of the first planetary gear set with the stationary member. 
     In yet another aspect of the present invention, the first torque-transmitting mechanism selectively interconnects a sun gear of the first planetary gear set and a sun of the second planetary gear set with the stationary member. 
     In yet another aspect of the present invention, the second torque-transmitting mechanism selectively interconnects a ring gear of the first planetary gear set with the stationary member. 
     In still another aspect of the present invention, the selective interconnection created by the first, second and fifth torque-transmitting mechanisms produce a reverse gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the first, second and third torque-transmitting mechanisms produce a first gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the first, second and fourth torque-transmitting mechanisms produce a second gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the second, third and fourth torque-transmitting mechanisms produce a third gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the second, fourth and fifth torque-transmitting mechanisms produce a fourth gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the second, third and fifth torque-transmitting mechanisms produce a fifth gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the third, fourth and fifth torque-transmitting mechanisms produce a sixth gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the first, third and fifth torque-transmitting mechanisms produce a seventh gear ratio. 
     In still another aspect of the present invention, the selective interconnection created by the first, fourth and fifth torque-transmitting mechanisms produce an eighth gear ratio. 
     The above features and advantages and other 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 
         FIG. 1  is a schematic representation of an embodiment of a transmission in accordance with the present invention; 
         FIG. 2  is a truth table listing the engaged torque-transmitting mechanisms for selected torque ratios achieved by the transmission of  FIG. 1 ; and 
         FIG. 3  is a lever diagram of the transmission of  FIG. 1  illustrating the power flow from the input through the gear sets to the output, in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components, in  FIG. 1  a multi-speed transmission  10  is depicted. The transmission  10  includes an input member  12  and an output member  14 . In the present embodiment, input member  12  and output member  14  are shafts, and will be referred to as such. Those skilled in the art will appreciate that the input and output members  12 ,  14  may be components other than shafts. The input shaft  12  is continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output shaft  14  is continuously connected with the final drive unit or transfer case (not shown). 
     Transmission  10  includes four planetary gear sets  16 ,  18 ,  20  and  22 . The planetary gear sets  16 ,  18 ,  20  and  22  are connected between the input shaft  12  and the output shaft  14 . In a preferred embodiment of the present invention, planetary gear set  16  is a simple planetary gear set that includes a sun gear member  24 , a ring gear member  26  and a carrier member  28  that rotatably supports a set of pinion gears  30  (only one shown). Sun gear member  24  is connected for common rotation with first outer shaft  32  and first intermediate shaft  34 . Ring gear member  26  is connected for common rotation with second outer shaft  36 . Pinion gears  30  are configured to intermesh with sun gear member  24  and ring gear member  26 . Carrier member  28  is connected for common rotation with second intermediate shaft  38 . 
     In a preferred embodiment of the present invention, planetary gear set  18  is a simple planetary gear set. More specifically, planetary gear set  18  includes a sun gear member  42 , a ring gear member  44  and a carrier member  46  that rotatably supports a set of pinion gears  48  (only one shown). Sun gear member  42  is connected for common rotation with first intermediate shaft  34 . Ring gear member  44  is connected for common rotation with a third intermediate shaft  50 . Carrier member  46  is connected for common rotation with an input shaft  12 . Pinion gears  48  are configured to intermesh with both sun gear member  42  and ring gear member  44 . 
     In a preferred embodiment of the present invention, planetary gear set  20  is a simple planetary gear set that includes a sun gear member  52 , a ring gear member  54  and a carrier member  56  that rotatably supports a set of pinion gears  58  (only one shown). Sun gear member  52  is connected for common rotation with a third intermediate shaft  50 . Ring gear member  54  is connected for common rotation with fourth intermediate shaft  60 . Carrier member  56  is connected for common rotation with fifth intermediate shaft  62 . Pinion gears  58  are configured to intermesh with both sun gear member  52  and ring gear member  54 . 
     In a preferred embodiment of the present invention, planetary gear set  22  is a simple planetary gear set that includes a sun gear member  72 , a ring gear member  74  and a carrier member  76  that rotatably supports a set of pinion gears  78  (only one shown). Sun gear member  72  is connected for common rotation with sixth intermediate shaft  64  and seventh intermediate shaft  66 . Ring gear member  74  is connected for common rotation with second intermediate shaft  38 . Carrier member  76  is connected for common rotation with an output shaft  14 . Pinion gears  78  are configured to intermesh with both sun gear member  72  and ring gear member  74 . 
     The transmission  10  includes a variety of torque-transmitting mechanisms or devices including a first intermediate clutch  80 , a second intermediate clutch  82 , a third intermediate clutch  84 , a first brake  90  and a second brake  92 . First intermediate clutch  80  is selectively engageable to connect seventh intermediate shaft  66  to carrier member  46  and input shaft  12 . Second intermediate clutch  82  is selectively engagable to connect sixth intermediate shaft  64  to sun gear member  52 . Third intermediate clutch  84  is selectively engagable to connect fourth intermediate shaft  60  to sixth intermediate shaft  64 . Brake  90  is selectively engageable to connect outer shaft  32  to transmission housing  100  to restrict rotation of shaft  32  relative to housing  100 . Brake  92  is selectively engageable to connect outer shaft  36  to housing  100  to restrict rotation of shaft  36  relative to housing  100 . 
     The transmission  10  is capable of transmitting torque from the input shaft  12  to the output shaft  14  in at least eight forward torque ratios and one reverse torque ratio as indicated in the truth table of  FIG. 2 . Each of the forward torque ratios and the reverse torque ratios is attained by engagement of one or more of the torque-transmitting mechanisms (i.e. first intermediate clutch  80 , a second intermediate clutch  82 , a third intermediate clutch  84 , a brake  90  and a brake  92 ). Those skilled in the art will readily understand that a different speed ratio is associated with each torque ratio. Thus, at least eight forward speed ratios and at least one reverse speed ratio may be attained by transmission  10 . An example of the gear ratios that may be obtained using the embodiments of the present invention are also shown in  FIG. 2 . Of course, other gear ratios are achievable depending on the gear diameter, gear tooth count and gear configuration selected. 
     A lever diagram  10 A is shown in  FIG. 3  that is representative of transmission  10  of  FIG. 1 , as well as the connections for the clutches  80 ,  82 ,  84  and brakes  90 ,  92 . The nodes  24 A,  26 A,  28 A,  42 A,  44 A,  46 A,  52 A,  54 A,  56 A,  72 A,  74 A and  76 A of the lever diagram  10 A represent the gear members  24 ,  26 ,  28 ,  42 ,  44 ,  46 ,  52 ,  54 ,  56 ,  72 ,  74  and  76  of  FIG. 1  such that the same numerical designation with the addition of an A suffix is used to identify the corresponding node. For example, the nodes  24 A and  42 A shown in  FIG. 3  represent sun gears  24  and  42  respectively shown in  FIG. 1 . Other components of  FIG. 3  have the same numbering convention for the corresponding components in  FIG. 1 . Moreover, the operation or engagement of clutches  80 ,  82 ,  84  and brakes  90 ,  92  to establish the various forward and reverse gear speeds will now be described with continuing reference to  FIGS. 1 ,  2  and  3 . 
     To establish the reverse torque ratio (Rev), the torque-transmitting mechanisms or clutches are selected as set forth in the table of  FIG. 2 . As shown in  FIG. 2 , first and second brakes  90 ,  92  and third intermediate clutch  84  are engaged to achieve the reverse torque ratio (Rev). 
     In neutral, none of the clutches or brakes are carrying torque. As noted in  FIG. 2 , in this gear state, the first and second brakes  90  and  92  are engaged but not carrying torque. 
     A first forward torque ratio (listed as 1st (first gear) in the truth table of  FIG. 2 ), is achieved by engaging first and second brakes  90  and  92  and first intermediate clutch  80 . An arrow is provided in  FIG. 2  that emanates from third intermediate clutch  84  that is released and points to the clutch that is engaged (clutch  80 ), when transitioning from reverse through neutral to first gear. 
     A subsequent forward torque ratio, indicated as 2 nd  (second gear) in  FIG. 2 , is established by engagement of first and second brakes  90 ,  92  and second intermediate clutch  82 . The shift from first gear to second gear occurs as follows: releasing first intermediate clutch  80  and engaging second intermediate clutch  82  while maintaining engagement of brakes  90 ,  92 . An arrow is provided in  FIG. 2  that emanates from the clutch that is released (clutch  80 ) and points to the clutch that is engaged (clutch  82 ). 
     The subsequent torque ratio, indicated as 3 rd  (third gear) in the truth table of  FIG. 2 , is established by the engagement of second brake  92 , first and second intermediate clutches  80  and  82 . The shift from second gear to third gear occurs as follows: clutch  82  and brake  92  remain engaged, brake  90  is released and clutch  80  is engaged. An arrow is provided in  FIG. 2  that emanates from the brake that is released (brake  90 ) and points to the clutch that is engaged (clutch  80 ). 
     The next subsequent forward torque ratio, indicated as 4 th  (fourth gear) in the truth table of  FIG. 2 , is established with the engagement of second brake  92 , second and third intermediate clutches  82 ,  84 . The shift from third gear to fourth gear is achieved as follows: engagement of clutch  82  and brake  92  are maintained, clutch  80  is released and clutch  84  is engaged. An arrow is provided in  FIG. 2  that emanates from the clutch that is released (clutch  80 ) and points to the clutch that is engaged (clutch  84 ). 
     A subsequent forward torque ratio indicated as 5 th  (fifth gear) in  FIG. 2 , is established with the engagement of second brake  92  and first and third intermediate clutches  80  and  84 . The shift from fourth gear to fifth gear occurs as follows: the engagement of clutch  84  and second brake  92  are maintained, clutch  82  is released and clutch  80  is engaged. An arrow is provided in  FIG. 2  that emanates from the clutch that is released (clutch  82 ) and points to the clutch that is engaged (clutch  80 ). 
     A subsequent forward torque ratio indicated as 6 th  (sixth gear), in the truth table of  FIG. 2 , is established with the engagement of first, second and third intermediate clutches  80 ,  82  and  84 . The shift from fifth gear to sixth gear occurs as follows: the engagement of clutches  80  and  84  are maintained, brake  92  is released and clutch  82  is engaged. An arrow is provided in  FIG. 2  that emanates from the brake that is released (brake  92 ) and points to the clutch that is engaged (clutch  82 ). 
     The next subsequent torque ratio, indicated as 7 th  (seventh gear) in the truth table of  FIG. 2 , is established with the engagement of brake  90  and first and third intermediate clutches  80 ,  84 . The shift from sixth gear to seventh gear occurs as follows: the engagement of clutches  80  and  84  are maintained, clutch  82  is released and brake  90  is engaged. An arrow is provided in  FIG. 2  that emanates from the clutch that is released (clutch  82 ) and points to the brake that is engaged (brake  90 ). 
     The next subsequent torque ratio, indicated as 8 th  (eight gear) in the truth table of  FIG. 2 , is established with the engagement of brake  90  and second and third intermediate clutches  82 ,  84 . The shift from seventh gear to eighth gear occurs as follows: the engagement of clutch  84  and brake  90  are maintained, clutch  80  is released and clutch  82  is engaged. An arrow is provided in  FIG. 2  that emanates from the clutch that is released (clutch  80 ) and points to the clutch that is engaged (clutch  82 ). 
     The present invention contemplates that downshifts follow the reverse sequence of the corresponding upshift (as described above), and several power-on skip-shifts that are single-transition are possible (e.g. from 1st to 3rd). 
     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: f