Patent Publication Number: US-2011067969-A1

Title: Non-rotating clutch

Description:
TECHNICAL FIELD 
     This disclosure relates to torque transmitting mechanisms for transmissions. 
     BACKGROUND OF THE INVENTION 
     Clutches are mechanisms for transmitting rotation, which can be engaged and disengaged. Friction clutches may have two sets of interleaved plates which are pressed into frictional engagement when actuated, causing common rotation (or lack of rotation, depending upon the viewpoint) between the sets of plates and members attached thereto. Generally, engagement allows torque to be transferred across the clutch, and disengagement does not allow torque transfer. 
     SUMMARY 
     A grounded clutch mechanism for a transmission is provided. The mechanism includes a transmission housing and a backing plate fixedly secured to the transmission housing. The backing plate has a plurality of backing plate posts. A plurality of reaction plates have a plurality of radially-outward spline teeth, which are configured to mate with the backing plate posts. Torque may be transferred between the backing plate and the reaction plates via the backing plate posts and the radially-outward spline teeth. The reaction plates do not transfer torque directly to the transmission housing. The transmission may have an axis of rotation defined therethrough, and the backing plate may be radially symmetric with respect to the axis of rotation. 
     The clutch mechanism may further include a plurality of clutch plates configured to selectively transfer torque to the plurality of reaction plates. The clutch plates may be configured to be selectively rotatable with respect to the axis of rotation and the reaction plates are configured not to be rotatable with respect to the axis of rotation. The backing plate may be formed from a ferritic material, and may be formed by a powdered metallurgy process. 
     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 and other embodiments for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic lever diagram illustration of an exemplary vehicle powertrain with a multi-mode, electrically-variable hybrid transmission in accordance with the present invention; 
         FIG. 2  is a schematic, side cross-sectional view of a non-rotating clutch and planetary gearset within the transmission; and 
         FIG. 3  is a schematic, partial exploded perspective view of the non-rotating clutch and transmission housing. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components throughout the several views, there is shown in  FIG. 1  a stick or lever diagram depiction of an exemplary vehicle powertrain system, designated generally as  10 . The powertrain  10  includes a restartable engine  12  that is selectively drivingly connected to, or in power flow communication with, a final drive system  16  via a multi-mode, electrically-variable hybrid-type power transmission  14 . 
     Those having ordinary skill in the art will recognize that a lever diagram is a schematic representation of the components of a mechanical device such as a transmission. Each individual lever represents a planetary gearset, 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 member, one for the planet gear carrier member, and one for the ring gear member. The relative length between the nodes of each lever may be used to represent the ring-to-sun ratio of each respective gearset. These lever ratios, in turn, are used to vary the gear ratios of the transmission in order to achieve appropriate ratios and ratio progression. 
     Mechanical couplings or interconnections between the nodes of the various planetary gear sets and other components of the transmission (such as motor/generators) are illustrated by thin, horizontal lines. Torque transmitting mechanisms such as clutches and brakes are presented as interleaved fingers. If the mechanism is a brake, one set of the fingers is grounded, or static. 
     The claimed invention is described herein in the context of a hybrid-type vehicular powertrain having a multi-mode, multi-speed, electrically-variable, hybrid transmission, which is intended solely as an illustrative application into which the present invention may be incorporated. The claimed invention is not limited to the particular powertrain arrangement shown in the drawings. Furthermore, the hybrid powertrain illustrated herein has been greatly simplified, as will be recognized by those having ordinary skill in the art. 
     The transmission  14  is designed to selectively receive at least a portion of its driving power from the engine  12 , through an input member  18 , for example. The transmission input member  18 , which is in the nature of a shaft, may be the engine output shaft (also referred to as a “crankshaft”). Alternatively, a damper (not shown) may be implemented between the engine  12  and the input member  18  of the transmission  14 . The engine  12  transfers power to the transmission  14 , which distributes torque through a transmission output member or shaft  20  to drive the final drive system  16 , and thereby propel the vehicle (not shown). 
     In the powertrain  10  depicted in  FIG. 1 , the engine  12  may be any of numerous forms of internal combustion engines, which includes spark-ignited gasoline engines and compression-ignited diesel engines. The engine  12  is readily adaptable to provide its available power to the transmission  14  at a range of operating speeds. 
     Referring still to  FIG. 1 , the hybrid transmission  14  utilizes one or more differential gear arrangements, such as three interconnected epicyclic planetary gear sets, designated generally at  24 ,  26  and  28 , respectively. The first, second, and third gear sets  24 ,  26 , and  28 , may alternatively be referred to as P 1 , P 2 , and P 3 , respectively. Each gear set includes three gear members: a first, second and third member. 
     The first, second and third gear sets may be counted “first” to “third” in any order in the drawings (e.g., left to right, right to left, etc.). Similarly, the first, second and third members of each gear set may be counted or identified as “first” to “third” in any order for each gear set in the drawings (e.g., top to bottom, bottom to top, etc.), in this description, and in the claims. 
     The first planetary gear set  24  has three gear members: a first, second and third member  30 ,  32  and  34 ; respectively. The first, second and third members may correspond to the first, second and third nodes of the lever diagram shown in  FIG. 1 , as viewed from top to bottom. The first member is an outer gear member (which may be referred to as a ring gear) that circumscribes the third member  34 , which may include an inner gear member (which may be referred to as a sun gear). 
     The second member  32  is a planet carrier. A plurality of planetary gear members (which may be referred to as pinion gears or planets) are rotatably mounted on the second member, planet carrier  32 . Through the planetary gear members, the planet carrier  32  is meshingly, or drivingly, engaged with both ring gear  30 , and sun gear  34 . 
     The second planetary gear set  26  also includes three gear members: a first, second and third member  40 ,  42  and  44 , respectively. The first member is a ring gear  40  which circumscribes the third member, a sun gear  44 . The ring gear  40  is coaxially aligned and rotatable with respect to the sun gear  44 . A plurality of planetary gear members are rotatably mounted on the second member, a planet carrier  42 , such that planet carrier  42  meshingly engages both the ring gear  40  and the sun gear  44 . 
     The third planetary gear set  28 , similar to the first and second gear sets  24 ,  26 , also has first, second and third members  50 ,  52  and  54 , respectively. In this arrangement, however, the second member  52 , shown on the middle node of the lever representing the third planetary gear set  28 , is the outer, ring gear. The ring gear  52  is coaxially aligned and rotatable with respect to the third member, sun gear  54 . The first member is a planet carrier  50  in this particular gear set, and is shown on the top node. A plurality of planetary or pinion gear members are rotatably mounted on the planet carrier  50 . Each of the pinion gear members is aligned to meshingly engage either the ring gear  52  and an adjacent pinion gear member or the sun gear  54  and an adjacent pinion gear member. 
     In the powertrain  10  shown in  FIG. 1 , the first and second planetary gear sets  24 ,  26  are simple planetary gear sets, whereas the third planetary gear set  28  is a compound planetary gear set. However, as will be recognized by those having ordinary skill in the art each of the planet carrier members described above can be either a single-pinion (simple) carrier assembly or a double-pinion (compound) carrier assembly. Embodiments with long pinions are also possible. 
     The first, second and third planetary gear sets  24 ,  26 ,  28  are compounded in that the second member  32  of the first planetary gear set  24  is connected to the second member  42  of the second planetary gear set  26  and the third member  54  of the third planetary gear set  28  by a central shaft  36 . As such, these three gear members  32 ,  42 ,  54  are rigidly attached for common rotation. 
     The engine  12  is continuously connected to the first member  30  of the first planetary gear set  24  by, for example, an integral hub plate  38 , for common rotation therewith. The third member  34  of the first planetary gear set  24  is continuously connected, for example, by a first sleeve shaft  46 , to a first motor/generator assembly  56 , which is also referred to herein as “motor A”. The third member  44  of the second planetary gear set  26  is continuously connected, for example, by a second sleeve shaft  48 , to a second motor/generator assembly  58 , also referred to herein as “motor B”. The second member  52  (the ring gear) of the third planetary gear set  28  is continuously connected to transmission output member  20  through, for example, an integral hub plate. The first and second sleeve shafts  46 ,  48  may circumscribe the central shaft  36 . 
     A first torque transmitting mechanism  70 —which is herein interchangeably referred to as clutch C 1 —selectively connects the first gear member  50  with a stationary member. The stationary member may be a transmission housing  60 , or may have an indirect connection to the transmission housing  60  or some other grounded object within the powertrain  10 . The second sleeve shaft  48 , and thus third member  44  and motor/generator  58 , is selectively connectable to the first member  50  of the third planetary gear set  28  through the selective engagement of a second torque transmitting mechanism  72 —which is herein interchangeably referred to as clutch C 2 . 
     A third torque transmitting mechanism  74 —which is herein interchangeably referred to as clutch C 3 —selectively connects the first gear member  40  of the second planetary gear set  26  to the transmission housing  60  or another stationary member. The first sleeve shaft  46 , and thus third gear member  34  and first motor/generator  56 , is also selectively connectable to the first member  40  of the second planetary gear set  26 , through selective engagement of a fourth torque transmitting mechanism  76 —which is herein interchangeably referred to as clutch C 4 . 
     A fifth torque transmitting mechanism  78 —which is herein interchangeably referred to as clutch C 5 —selectively connects the input member  18  of engine  12  and the first gear member  30  of the first planetary gear set  24  to the transmission housing  60  or another stationary member. Clutch C 5  is an input brake clutch, which selectively locks the input member  18  when engine  12  is off. Locking input member  18  provides more reaction for regenerative braking energy. 
     The first and second torque transmitting mechanisms  70 ,  72  (C 1  and C 2 ) may be referred to as “output clutches.” The third and fourth torque transmitting mechanisms  74 ,  76  (C 3  and C 4 ) may be referred to as “holding clutches”. The term “clutch” may be used to refer generally to any of the torque transmitting mechanisms, including, without limitation, devices commonly referred to as clutches, brakes, non-rotating or grounded clutches, et cetera. 
     In the exemplary embodiment depicted in  FIG. 1 , the various torque transmitting mechanisms  70 ,  72 ,  74 ,  76 ,  78  (C 1 -C 5 ) are all friction clutches. However, other conventional clutch configurations may be employed, such as dog clutches, rocker clutches, and others recognizable to those having ordinary skill in the art. The clutches C 1 -C 5  may be hydraulically actuated, receiving pressurized hydraulic fluid from a pump (not shown). Hydraulic actuation of clutches C 1 -C 5  is accomplished, for example, by using a conventional hydraulic fluid control circuit, as will be recognized by one having ordinary skill in the art. 
     The planetary gear sets  24 ,  26 ,  28 , as well as the first and second motor/generators  56 ,  58  (motors A and B) are coaxially oriented about the intermediate central shaft  36 , which forms an axis of rotation  37  for the transmission  14 . Motor A or motor B may take on an annular configuration, permitting one or both to generally circumscribe the three planetary gear sets  24 ,  26 ,  28  and the axis of rotation  37 . 
     The hybrid transmission  14  receives torque from a plurality of torque-generative devices. “Torque-generative devices” include the engine  12  and the motors/generators  56 ,  58  as a result of energy conversion from fuel stored in a fuel tank or electrical potential stored in an electrical energy storage device (neither of which is shown). 
     The engine  12 , motor A ( 56 ) and motor B ( 58 ) may operate individually or in concert—in conjunction with the planetary gear sets and selectively-engageable torque-transmitting mechanisms—to rotate the transmission output shaft  20 . Moreover, motor A and motor B are preferably configured to selectively operate as both a motor and a generator. For example, motor A and motor B are capable of converting electrical energy to mechanical energy (e.g., during vehicle propulsion), and further capable of converting mechanical energy to electrical energy (e.g., during regenerative braking or during periods of excess power supply from engine  12 ). 
     Referring now to  FIGS. 2 and 3 , and with continued reference to  FIG. 1 , there are shown two partial views of the interior of transmission  14 .  FIG. 2  shows a schematic side view of the first torque transmitting mechanism  70 , C 1 , and the third planetary gearset  28  within the transmission  14 .  FIG. 3  shows a partial exploded view of the clutch C 1 . 
     In the transmission  14 , C 1  is the rear non-rotating clutch—a clutch with non-rotating reaction plates, also referred to as a brake, grounded clutch, or grounded torque transmitting mechanism. In powertrain  10 , C 1  may experience torque reversals under certain conditions. For example, and without limitation: a throttle position change from partial throttle to no throttle during a low speed, down-grade vehicle maneuver will reverse the torque direction on the applied clutch C 1 . 
     The clutch C 1  includes a backing plate  80  which is fixedly secured to the transmission housing  60 . A pattern or plurality of backing plate posts  82  extend in the axial direction from the backing plate  80 , toward the transmission housing  60 . A plurality of bolt holes  84  are defined axially through the plurality of backing plate posts  82 . The bolt holes  84  may be configured to pass through the middle or center of the backing plate posts  82 . A plurality of backing plate bolts  86  pass through the bolt holes  84  and thread into threaded holes  88  in the transmission housing  60 , such that the backing plate  80  can be rigidly attached to the transmission housing  60 . 
     The backing plate posts  82  serve to set the axial position of the backing plate  80  to the transmission housing  60 , eliminating the need for a retaining ring to hold the backing plate  80  relative to the remainder of clutch C 1 . A plurality of reaction plates  90  are located between the backing plate posts  82 . The reaction plates  90  have a plurality of radially-outward spline teeth  92 . 
     Since the backing plate  80  is bolted to the transmission housing  60 , and is therefore a static (non-rotating) object, the radially-outward spline teeth  92  can be mated directly to the backing plate posts  82 . Once assembled, the reaction plates  90  are splined to the backing plate posts  82 , in lieu of being splined to teeth formed on the interior of the transmission housing  60 . Therefore, the reaction plates  90  are grounded by the backing plate  80 , as opposed to the transmission housing  60 , and torque may be transferred between the backing plate  80  and reaction plates  90 . 
     A plurality of clutch plates  94  rotate in common with the planet carrier  50  of the third planetary gearset  28 . In operation of the transmission  10 , actuation of C 1  causes the clutch plates  94  to transfer torque to the plurality of reaction plates  90 . Therefore, actuation of the clutch plates  94  cause the planet carrier  50  to become grounded by the backing plate  80  and to stop rotating relative to the transmission housing  60 . 
     The backing plate  80  is radially symmetric with respect to the axis of rotation  37 . Therefore, the backing plate posts  82 , bolt holes  84 , and radially-outward spline teeth  92  are on a repetitive symmetrical pattern.  FIG. 3  shows a radially-symmetric pattern of, for example, and without limitation: twelve backing plate posts  82 , twelve bolt holes  84 , and twelve radially-outward spline teeth  92 . The reaction plates are also axially symmetric, so the reaction plates  90  can be assembled in to the backing plate  80  in any of 24 orientations (twelve radial rotations and two axial directions). Furthermore, the backing plate  80  (with the clutch plates  94  and reaction plates  90  already in place) can be assembled in any of twelve orientations into the transmission housing  60 . 
     Those having ordinary skill in the art will recognize that different patterns and different numbers of elements may be used, depending upon the exact design. Furthermore, those having ordinary skill in the art will recognize that absolute symmetry is not required (manufacturing imperfections may occur, for example). 
     An alternative non-rotating clutch (not shown) may be directly grounded to the transmission housing  60  by a pattern of external spline teeth on the reaction plates and internal spline teeth formed directly on the transmission housing  60 . These internal spline teeth may be cast into the transmission housing  60  or machined into the transmission housing  60  after the casting process. 
     The backing plate  80  may be formed from of a ferrite material, and may be formed by (for example, and without limitation) a powdered metallurgy process. The relative strength of ferritic materials forming the backing plate  80  as compared to the aluminum forming the transmission housing  60  may require fewer radially-outward spline teeth  92  to react the clutch torque. Furthermore, the thickness of the reaction plates  90  may be reduced, as less area is required to distribute stress between the radially-outward spline teeth  92  and the static member. 
     Torque reversals on non-rotating clutch cause the radially-outward spline teeth  92  to transfer torque from one backing plate post  82  to another. If the internal spline teeth were formed on the transmission housing  60 , this torque transfer may cause the radially-outward spline teeth  92  to travel from their clockwise seat position against the internal spline teeth to their counter-clockwise position against the internal spline teeth, or vice versa. This travel of reaction plates is termed backlash or snap, and may cause vibrations at the interfaces between the backing plate posts  82  and the radially-outward spline teeth  92 , resulting in radiated audible noise outside of the transmission  14 . 
     The clearance between the internal spline teeth—either those incorporated into the backing plate posts  82  or on the interior of transmission housing  60 —and the spline teeth of the reaction plates  90  determines the amount of travel during torque reversals, and may, therefore, affect the amount of noise energy generated during the same event. In alternative configurations, the torque reversals of the reaction plates may also rotate the clutch backing plate, which is simply an axial space-holder and support held in place by a retaining ring. 
     Forming the backing plate posts  82  from powdered metal does not require casting draft and may have a lower location tolerance requirement than the aluminum transmission housing  60 , which is likely a die-cast component. By reducing the location tolerance between the radially-outward splines and the interior splines—which are formed on the backing plate posts  82  in this clutch C 1 —reduces the amount of the backlash and the noise levels in the non-rotating clutch. Furthermore, since the non-rotating splines are on an internal component—the backing plate posts  82  of the backing plate  80 , as opposed to an external component, the transmission housing  60 —the noise radiated outside of the transmission  14  may be reduced due to damping characteristics of the components as vibration travels through to the external transmission housing  60 . 
     The present invention is described in detail with respect to automotive applications; however, those skilled in the art will recognize the broader applicability of the invention. Those having ordinary skill in the art will further recognize that terms such as “above,” “below,” “upward,” “downward,” et cetera, are used descriptively of the figures, and do not represent limitations on the scope of the invention, as defined by the appended claims. While the best modes and other embodiments for carrying out the claimed 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.