Patent Abstract:
A transmission is provided having an input member, an output member, two planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices include clutches, centrifugal clutches, and synchronizers.

Full Description:
FIELD 
       [0001]    The invention relates generally to a multiple speed transmission having a plurality of planetary gear sets and a plurality of torque transmitting devices, and more particularly to a transmission having three speeds, two planetary gear sets and a plurality of torque transmitting devices. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
         [0003]    A typical multiple speed transmission uses a combination of friction clutches, planetary gear arrangements and fixed interconnections to achieve a plurality of gear ratios. The number and physical arrangement of the planetary gear sets, generally, are dictated by packaging, cost and desired speed ratios. 
         [0004]    While current transmissions achieve their intended purpose, the need for new and improved transmission configurations which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness and improved packaging, primarily reduced size and weight, is essentially constant. Accordingly, there is a need for an improved, cost-effective, compact multiple speed transmission. 
       SUMMARY 
       [0005]    A low content transmission is provided having an input member, an output member, two planetary gear sets, a plurality of coupling members and a plurality of torque transmitting devices. Each of the planetary gear sets includes first, second and third members. The torque transmitting devices are for example synchronizers and clutches. 
         [0006]    In one embodiment, the transmission includes an input member, an output member, an intermediate member, and first and second planetary gear sets each having first, second and third members, wherein the output member is connected to the second member of the first planetary gear set and the first member of the second planetary gear set. An interconnecting member continuously interconnects the third member of the first planetary gear set with the second member of the second planetary gear set. A first synchronizer is selectively engageable to interconnect the input member with the first member of the first planetary gear set. A second synchronizer is selectively engageable to interconnect the input member with the third member of the second planetary gear set. A first clutch which could be a controllable one-way clutch is selectively engageable to interconnect at least one of the third member of the first planetary gear set and the second member of the second planetary gear set with a stationary member. A second clutch which could be a one-way clutch is engageable to interconnect the third member of the second planetary gear set with the intermediate member. A first centrifugal clutch is selectively engageable to interconnect the intermediate member with the stationary member. A second centrifugal clutch is selectively engageable to interconnect at least one of the output member, the second member of the first planetary gear set, and the first member of the second planetary gear set with the third member of the second planetary gear set. The first and second synchronizers, the first and second clutches, and the first and second centrifugal clutches are engageable in combinations of at least two to establish at least three forward speed ratios and at least one reverse speed ratio between the input member and the output member. 
         [0007]    In one aspect of the present invention, the first member of the first planetary gear set and the third member of the second planetary gear set are sun gear members, the second members of the first and second planetary gear sets are carrier members, and the third member of the first planetary gear set and the first member of the second planetary gear set are ring gear members. 
         [0008]    In another aspect of the present invention, the first centrifugal clutch includes a first centrifugal clutch flyweight interconnected to the output member and the second centrifugal clutch includes a second centrifugal clutch flyweight interconnected to the output member. 
         [0009]    In yet another aspect of the present invention, the reverse speed ratio is provided when the second synchronizer and the first clutch are engaged or activated. 
         [0010]    In yet another aspect of the present invention, a first of the at least three forward speed ratios is provided when the first synchronizer, the first clutch, and the second clutch are engaged or activated. 
         [0011]    In yet another aspect of the present invention, a second of the at least three forward speed ratios is provided when the first synchronizer, the second clutch, and the first centrifugal clutch are engaged or activated. 
         [0012]    In yet another aspect of the present invention, a third of the at least three forward speed ratios is provided when the first synchronizer, the first centrifugal clutch, and the second centrifugal clutch are engaged or activated. 
         [0013]    Further objects, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature. 
     
    
     
       DRAWINGS 
         [0014]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0015]      FIG. 1  is a lever diagram of an embodiment of a three speed transmission according to the present invention; 
           [0016]      FIG. 2  is a diagrammatic view of an embodiment of a three speed transmission according to the present invention; 
           [0017]      FIG. 3  is a truth table presenting the state of engagement of the various torque transmitting mechanisms in each of the available forward and reverse speeds or gear ratios of the transmission illustrated in  FIGS. 1 and 2 ; 
           [0018]      FIG. 4  is a diagrammatic view of an embodiment of the three speed transmission according to the present invention in a reverse gear ratio; 
           [0019]      FIG. 5  is a diagrammatic view of an embodiment of the three speed transmission according to the present invention in a first gear ratio; 
           [0020]      FIG. 6  is a diagrammatic view of an embodiment of the three speed transmission according to the present invention in a second gear ratio; and 
           [0021]      FIG. 7  is a diagrammatic view of an embodiment of the three speed transmission according to the present invention in a third gear ratio. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0023]    Referring now to  FIG. 1 , an embodiment of a three speed transmission  10  is illustrated in a lever diagram format. A lever diagram is a schematic representation of the components of a mechanical device such as an automatic transmission. Each individual lever represents a planetary gear set wherein the three basic mechanical components of the planetary gear are each represented by a node. Therefore, a single lever contains three nodes: one for the sun gear, one for the planet gear carrier, and one for the ring gear. The relative length between the nodes of each lever can be used to represent the ring-to-sun ratio of each respective gear set. These lever ratios, in turn, are used to vary the gear ratios of the transmission in order to achieve an appropriate ratios and ratio progression. Mechanical couplings or interconnections between the nodes of the various planetary gear sets are illustrated by thin, horizontal lines and torque transmitting devices such as clutches and brakes are presented as interleaved fingers. Further explanation of the format, purpose and use of lever diagrams can be found in SAE Paper 810102, “The Lever Analogy: A New Tool in Transmission Analysis” by Benford and Leising which is hereby fully incorporated by reference. 
         [0024]    The transmission  10  includes an input shaft or member  12 , a lever that represents two planetary gear sets including a first planetary gear set  14  and a second planetary gear set  16 , and an output shaft or member  18 . The first planetary gear set  14  includes three nodes: a first node  14 A, a second node  14 B, and a third node  14 C. The second planetary gear set  16  includes three nodes: a first node  16 A, a second node  16 B, and a third node  16 C. The second node  14 B of the first planetary gear set  14  and the first node  16 A of the second planetary gear set  16  are represented as a single node, indicated by reference designation  14 B/ 16 A in  FIG. 1  and the third node  14 C of the first planetary gear set  14  and the second node  16 B of the second planetary gear set  16  are represented by a single node, indicated by reference designation  14 C/ 16 B in  FIG. 1 . 
         [0025]    The transmission  10  further includes a synchronizer assembly  20  that includes a first synchronizer or dog clutch  20 A and a second synchronizer or dog clutch  20 B. The first synchronizer or dog clutch  20 A selectively connects the input member  12  with the first node  14 A of the first planetary gear set  14 . The second synchronizer or dog clutch  20 B selectively connects the input member  12  with the third node  16 C of the second planetary gear set  16 . A first clutch  22  selectively connects the third node  14 C of the first planetary gear set  14  and the second node  16 B of the second planetary gear set  16  with a ground, stationary member, or a transmission housing  40 . A second clutch  24  connects the third node  16 C of the second planetary gear set  16  with an intermediate shaft or member  26 . A first centrifugal clutch  28  selectively connects the intermediate shaft or member  26  with the ground, the stationary member, or the transmission housing  40 . A second centrifugal clutch  30  selectively connects the third node  16 C of the second planetary gear set  16  with the second node  14 B of the first planetary gear set  14 , the first node  16 A of the second planetary gear set  16 , and the output shaft or member  18 . 
         [0026]    Referring now to  FIG. 2 , a stick diagram presents a schematic layout of the embodiment of the three speed transmission  10  according to the present invention. In  FIG. 2 , the numbering from the lever diagram of  FIG. 1  is carried over. The synchronizers, clutches, centrifugal clutches, and intermediate member are correspondingly presented whereas the nodes of the planetary gear sets now appear as components of planetary gear sets such as sun gears, ring gears, planet gears and planet gear carriers. 
         [0027]    For example, the planetary gear set  14  includes a sun gear member  14 A, a ring gear member  14 C and a planet gear carrier member  14 B that rotatably supports a set of planet gears  14 D (only one of which is shown). The sun gear member  14 A is connected for common rotation with a first shaft or interconnecting member  42 . The ring gear member  14 C is connected for common rotation with a second shaft or interconnecting member  44 . The planet carrier member  14 B is connected for common rotation with the output member  18  and a third shaft or interconnecting member  46 . The planet gears  14 D each are configured to intermesh with both the sun gear member  14 A and the ring gear member  14 C. 
         [0028]    The planetary gear set  16  includes a sun gear member  16 C, a ring gear member  16 A and a planet gear carrier member  16 B that rotatably supports a set of planet gears  16 D (only one of which is shown). The sun gear member  16 C is connected for common rotation with a fourth shaft or interconnecting member  48  and a fifth shaft or interconnecting member  50 . The ring gear member  16 A is connected for common rotation with the output shaft or member  18 . The planet carrier member  16 B is connected for common rotation with the third shaft or interconnecting member  44  and with a sixth shaft or interconnecting member  52 . The planet gears  16 D each are configured to intermesh with both the sun gear member  16 C and the ring gear member  16 A. 
         [0029]    The input shaft or member  12  is continuously connected to an engine (not shown) or to a turbine of a torque converter (not shown). The output shaft or member  18  is continuously connected with the final drive unit or transfer case (not shown). 
         [0030]    The various torque transmitting mechanisms including the synchronizer assembly  20 , the clutches  22 ,  24 , and the centrifugal clutches  28 ,  30  allow for selective interconnection of the shafts or interconnecting members, members of the planetary gear sets and the housing. For example, the synchronizer assembly  20  includes a collar  56  that is operable to translate an actuator or shift fork between left and right positions, thereby actuating the first synchronizer  20 A and the second synchronizer  20 B. The first synchronizer  20 A is engageable to connect the first shaft or interconnecting member  42  with the input shaft or member  12 . The second synchronizer  20 B is engageable to connect the fourth shaft or interconnecting member  48  with the input shaft or member  12 . 
         [0031]    The first clutch  22  could be a typical brake clutch or a controllable one-way clutch. The controllable one-way clutch would be required to hold torque in both directions in one state and to hold torque in one direction and overrun in the other direction for the other state. The second clutch  24  could be a conventional one-way clutch that transmits torque in one rotational direction only. The first clutch  22  is engageable to connect the sixth shaft or interconnecting member  52  with the ground, stationary member, or transmission housing  40  in order to restrict the movement of the sixth interconnecting member  52  relative to the transmission housing. The second clutch  24  is engageable to connect the fifth shaft or interconnecting member  50  with the intermediate member  26  when the fifth shaft or interconnecting member  50  rotates in a direction that engages the second clutch  24 . 
         [0032]    The centrifugal clutches  28 ,  30  use centrifugal force to compel weighted arms or flyweights to swing outward and force the clutch to engage. The clutches are disengaged using gear thrust. More specifically, the first centrifugal clutch  28  includes a flyweight  58  that is rotationally coupled to the output shaft or member  18 . When in a released condition, as illustrated in  FIGS. 4 and 5 , the flyweight  58  does not engage the first centrifugal clutch  28 . When the output member  18  and therefore the flyweight  58  reach a predetermined rotational speed, the flyweight  58  pivots or otherwise moves and engages the first centrifugal clutch  28 , as illustrated in  FIGS. 2 ,  6  and  7 . When engaged, the first centrifugal clutch  28  connects the intermediate member  26  to the ground, stationary member, or transmission housing  40  in order to restrict the movement of the intermediate member  26  relative to the transmission housing  40 . A spring, not shown, disengages the first centrifugal clutch  28  when the rotational speed of the output member  18  decreases such that the flyweight  58  returns to the rest position. The second centrifugal clutch  30  includes a flyweight  60  that is rotationally coupled to the output shaft or member  18 . When in a released condition, as illustrated in  FIGS. 4-6 , the flyweight  60  does not engage the first centrifugal clutch  30 . When the output member  18  and therefore the flyweight  60  reach a predetermined rotational speed that is larger than the rotational speed required to move the flyweight  58 , the flyweight  60  pivots or otherwise moves and engages the second centrifugal clutch  30 , as illustrated in  FIGS. 2 and 7 . When engaged, the second centrifugal clutch  30  connects the third shaft or interconnecting member  46  with the fourth shaft or interconnecting member  48 . A spring, not shown, disengages the second centrifugal clutch  30  when the rotational speed of the output member  18  decreases such that the flyweight  60  returns to the rest position. 
         [0033]    Referring now to  FIGS. 3-7 , the operation of the embodiment of the three speed transmission  10  will be described. It will be appreciated that transmission  10  is capable of transmitting torque from the input shaft or member  12  to the output shaft or member  18  in at least three forward speed or torque ratios and at least one reverse speed or torque ratio. Each forward and reverse speed or torque ratio is attained by engagement of one or more of the torque-transmitting mechanisms (i.e. first synchronizer  20 A, second synchronizer  20 B, first clutch  22 , second clutch  24 , first centrifugal clutch  28 , and second centrifugal clutch  30  ), as will be explained below.  FIG. 3  is a truth table presenting the various combinations of torque-transmitting mechanisms that are activated or engaged to achieve the various gear states. An “X” in the box means that the particular synchronizer or clutch is engaged to achieve the desired gear state. An “O” represents that the particular torque transmitting mechanism is on or active, but not carrying torque. Actual numerical gear ratios of the various gear states are also presented although it should be appreciated that these numerical values are exemplary only and that they may be adjusted over significant ranges to accommodate various applications and operational criteria of the transmission  10 . An example of the gear ratios that may be obtained using the embodiments of the present invention are also shown in  FIG. 3 . Of course, other gear ratios are achievable depending on the gear diameter, gear teeth count and gear configuration selected. 
         [0034]    With reference to  FIG. 3  and  FIG. 4 , to establish a reverse gear, the second synchronizer  20 B and the first clutch  22  are engaged or activated. The second synchronizer  20 B connects the fourth shaft or interconnecting member  48  with the input shaft or member  12 . The first clutch  22  connects the sixth shaft or interconnecting member  52  with the ground, stationary member, or transmission housing  40  in order to restrict the movement of the sixth interconnecting member  52  relative to the transmission housing  40 . 
         [0035]    With reference to  FIG. 3  and  FIG. 5 , to establish a first gear, the first synchronizer  20 A, the first clutch  22 , and the second clutch  24  are engaged or activated. The first synchronizer  20 A connects the first shaft or interconnecting member  42  with the input shaft or member  12 . The first clutch  22  connects the sixth shaft or interconnecting member  52  with the ground, stationary member, or transmission housing  40  in order to restrict the movement of the sixth interconnecting member  52  relative to the transmission housing  40 . The second clutch  24  connects the fifth shaft or interconnecting member  50  with the intermediate member  26 . However, since the second centrifugal clutch  28  is not engaged or activated, the intermediate member  26  is not coupled to ground. 
         [0036]    With reference to  FIG. 3  and  FIG. 6 , to establish a second gear, the first synchronizer  20 A, the second clutch  24 , and the first centrifugal clutch  28  are engaged or activated. The first synchronizer  20 A connects the first shaft or interconnecting member  42  with the input shaft or member  12 . The second clutch  24  connects the fifth shaft or interconnecting member  50  with the intermediate member  26 . Sufficient rotation of the output member  18  pivots or moves the flyweight  58  thereby engaging the first centrifugal clutch  28 . When engaged, the first centrifugal clutch  28  connects the intermediate member  26  to the ground, stationary member, or transmission housing  40  in order to restrict the movement of the intermediate member  26  relative to the transmission housing  40 . 
         [0037]    With reference to  FIG. 3  and  FIG. 7 , to establish a third gear, the first synchronizer  20 A, the first centrifugal clutch  28 , and the second centrifugal clutch  30  are engaged or activated. The first synchronizer  20 A connects the first shaft or interconnecting member  42  with the input shaft or member  12 . Sufficient rotation of the output member  18  pivots or moves the flyweight  58  thereby engaging the first centrifugal clutch  28 . When engaged, the first centrifugal clutch  28  connects the intermediate member  26  to the ground, stationary member, or transmission housing  40  in order to restrict the movement of the intermediate member  26  relative to the transmission housing  40 . However, the second clutch  24  is overrunning and not connecting the intermediate member  26  to the sun gear  16 C of the second planetary gear set. Sufficient rotation of the output member  18  pivots or moves the flyweight  60  thereby engaging the second centrifugal clutch  30 . When engaged, the second centrifugal clutch  30  connects the third shaft or interconnecting member  46  with the fourth shaft or interconnecting member  48 . 
         [0038]    It will be appreciated that the foregoing explanation of operation and gear states of the eight speed transmission  10  assumes, first of all, that all the synchronizers and clutches not specifically referenced in a given gear state are inactive or disengaged and, second of all, that during gear shifts, i.e., changes of gear state, between at least adjacent gear states, a synchronizer or clutch engaged or activated in both gear states will remain engaged or activated. 
         [0039]    The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

Technology Classification (CPC): 5