Patent Publication Number: US-2011048889-A1

Title: Clutch Plate Having Reinforced Spline Teeth

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a non-provisional claiming priority under 35 USC §119 (e) to U.S. Provisional Patent Application No. 61/238,340 filed on Aug. 31, 2009. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to torque transmission components, and more particularly relates to clutch plates. 
     BACKGROUND OF THE DISCLOSURE 
     Torque transmission members such as clutch plates are widely known in the art. In vehicles, for example, various types of clutches have been used to transmit torque, such as an automatic transmission which may use multiple clutches to engage or disengage selected gearsets, thereby to obtain a desired gear ratio. The clutches provided for this purpose are typically friction plate clutches, which include a plurality of inner or drive plates that are splined to a rotatable hub. A housing or case is coaxially aligned with the hub and supported for rotation independent of the hub. A plurality of outer or driven plates are splined to the housing or case and are interposed between the drive plates, such that the drive and driven plates are alternately arranged on a common axis. The drive plates include a friction material on one or both sides of the plates. An actuator, such as a hydraulic piston, applies a pressure force that presses the drive and driven plates into engagement, thereby permitting torque to be transferred from the hub to the housing. 
     The above-described clutch plates typically use spline teeth to couple the plate to an associated rotatable member. The spline teeth are configured to slide along grooves formed in the rotatable member. Additionally, the spline teeth provide the points of contact between the clutch plate and the rotatable member, and therefore they encounter a significant amount of contact stress. In most conventional clutch plates, the spline teeth are formed as extensions of a central, annular body. Accordingly, the thickness of the entire clutch plate is typically selected according to the amount of contact stress expected at the spline teeth. This may result in the body portion of the clutch plate being oversized, which may increase clutch plate weight and rotating inertia, thereby adversely impacting clutch design. Additionally, thicker clutch plates may require additional space, thereby increasing the size of the transmission or other component in which they are used. 
     SUMMARY OF THE DISCLOSURE  
     In accordance with one aspect the disclosure, a clutch plate is provided for transmitting torque from a driving member to a driven member. The clutch plate may include an annular body disposed around an axis and defining inner and outer edges, the annular body having a thickness “t”. A plurality of spline teeth may project radially from the annular body, each spline tooth including a tab extending from the annular body and a flap superposed over the tab, in which each spline tooth has a thickness “T” approximately twice the body thickness “t”. 
     According to other aspects of this disclosure, a clutch plate may include an annular body disposed around an axis and defining inner and outer edge, and a plurality of spline teeth projecting radially from the annular body. Each spline tooth may have a tab extending from the annular body, a flap superposed over the tab, and a joint extending between the tab and the flap. The joint may define a fold line extending substantially circumferentially about the body axis. 
     According to further aspects of this disclosure a clutch plate may include an annular body disposed around an axis and defining inner and outer edges, the annular body having a thickness “t”, and a plurality of spline teeth projecting radially from the annular body. Each spline tooth may have a tab aligned with and extending from one of the inner and outer edges of the annular body, each tab including first and second side edges, a flap superposed over the tab so that each spline tooth has a thickness “T” approximately twice the body thickness “t”, each flap including first and second side edges, and a joint extending between the tab and the flap, the joint defining a fold line extending substantially circumferentially about the body axis. Each tab and flap have substantially the same overall shape so that each spline tooth includes a first composite side edge formed by the tab first edge and flap first edge and a second composite side edge formed by the tab second side edge and the flap second side edge. 
     These and other aspects and features of the disclosure will become more apparent upon reading the following detailed description when taken into consideration in conjunction with the accompanied drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a clutch assembly including inner and outer clutch plates constructed according to the present disclosure. 
         FIG. 2  is a plan view of an inner clutch plate used in the clutch assembly of  FIG. 1 . 
         FIG. 3  is a side elevation view, in cross-section, of a portion of the inner clutch plate taken along line  3 - 3  of  FIG. 2 . 
         FIG. 4  is a plan view of an outer clutch plate used in the clutch assembly of  FIG. 1 . 
         FIG. 5  is a perspective view, in partial cross-section, of the outer clutch plate taken along line  5 - 5  of  FIG. 4 . 
     
    
    
     While the present disclosure is susceptible to various modifications and alternative constructions, certain illustrative embodiments thereof are shown in the drawings and are described below in detail. It should be understood, however, that there is no intention to limit the present disclosure to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit of the scope of the present disclosure. 
     DETAILED DESCRIPTION 
     A clutch plate is disclosed herein that includes reinforced spline teeth. The clutch plate includes a body portion having a thickness, and the spline teeth have a thickness that is approximately twice the thickness of the body portion. In certain embodiments, each spline tooth may include a tab portion and a flap portion that is superposed over the tab portion. The flap portion may be joined to the tab portion by a circumferential fold line. The increased thickness of the spline teeth reduces contact stress in the spline teeth while permitting a reduced thickness body portion, thereby reducing overall clutch plate weight and associated rotating inertia to improve clutch performance. Additionally, the smaller body portion thickness reduces the amount of space required for the torque transmission component in which the clutch plate is used. 
     Referring now to the drawings,  FIG. 1  provides a schematic representation of a clutch assembly  20  used in a torque transmission component, such as an automatic transmission  22  for a vehicle. It is to be understood that the automatic transmission  22  is but one example of the setting in which the clutch assembly  20  may be used. Other areas of a transmission, vehicle, machine tool, or other machine could also advantageously employ its teachings as will be readily understood by one of ordinary skill in the art. 
     As shown in  FIG. 1 , the transmission  22  may include a drive shaft  24  adapted to rotate about an axis  26 , which is itself powered by the motive force of an engine (not shown) of a vehicle (also not shown). A hub  28  is attached to and rotates with the drive shaft  24 . The hub  28  may be provided as a simple annular flange coupled to the drive shaft  24  or it may be configured to provide additional features or capabilities, such as a one-way clutch. An exterior peripheral surface of the hub  28  may be formed with grooves  30 . The transmission  22  may also include a case or housing  32  which is mounted coaxially with the drive shaft  24  and is supported for rotation about the axis  26  independent of the drive shaft  24 . The housing  32  may also be formed with grooves  33 . According to this embodiment, the drive shaft  24  is the driving or input member while the housing  32  is the driven or output member. 
     Referring still to  FIG. 1 , the clutch assembly  20  may include a plurality of clutch plates which use friction to transfer torque from the hub  28  to the housing  32 . One or more inner clutch plates  38  may be slidably coupled to the hub  28 . Each inner clutch plate  38  may include friction surfaces  40  on both sides of the plate. Alternatively, only one side of each inner friction plate may include a friction surface  40 . Additionally, one or more outer clutch plates  42  may be slidably coupled to the housing  32  and positioned such that each outer clutch plate  42  is disposed between adjacent inner clutch plates  38 . Each outer clutch plate  42  may include a friction surface on one or both sides of the plate. 
     The inner and outer clutch plates  38 ,  42  are allowed to slide in an axial direction while remaining attached to and rotating with the hub  28  and housing  32 , respectively. Accordingly, the plates  38 ,  42  are movable between an unengaged position, in which the plates  38 ,  42  do not contact each other, and a torque transmitting position, in which the plates  38 ,  42  engage each other with sufficient force to transmit torque from the inner plates  38  to the outer plates  42 . An actuator  44  may be operatively coupled to the clutch plates  38 ,  42  to move them between the unengaged and torque transmitting positions. 
     The inner clutch plate  38  is shown in greater detail in  FIGS. 2 and 3 . In the illustrated embodiment, the inner clutch plate  38  includes an annular body  50  disposed around an axis  52 . The body  50  includes an inner edge  54  and an outer edge  56 . A plurality of spline teeth  58  project inwardly from the body inner edge  54  and are configured to slidably engage the grooves  30  formed in the hub  28 . As best shown in  FIG. 3 , the body  50  has a thickness “t”. 
     Each spline tooth  58  may have a greater thickness than the body  50  to reduce contact stresses during torque transmission. In the illustrated embodiment, each spline tooth  58  includes a tab  60  and a flap  62 . The tab  60  may be aligned with and extend inwardly from the body  50 . The flap  62  is superposed over the tab  60 . The tab  60  and flap  62  may be coupled by a joint  64  that defines a fold line  66  extending circumferentially about the body axis  52 . The tab  60  and flap  62 , therefore, may be formed integrally with the body  50 , with the flap  62  being folded over to overlie the tab  60 . Accordingly, each spline tooth  58  may have a thickness “T” that is approximately twice the body thickness “t”. 
     One of the spline teeth  58  is shown in  FIG. 2  prior to the flap  62  being folded over the tab  60 . According to the illustrated embodiment, the tab  60  includes first and second side edges  68 ,  70 . The fold line  66  forms a circumferential inner edge of the tab  60 . The flap  62  similarly has first and second side edges  72 ,  74 . The fold line  66  may form a circumferential outer edge of the flap  62 . The tab  60  and flap  62  may be formed with substantially identical shapes. In the illustrated embodiment, the tab  60  and flap  62  have an involute gear shape, with the side edges having arcuate shapes that taper inwardly toward the fold line  66 . Alternatively, the tab  60  and flap  62  may have straight-tooth gear shapes, or other alternative shapes suitable for transmitting rotation to or from the associated shaft. 
     When the flap  62  is folded over the tab  60 , the resulting spline tooth  58  has first and second composite side edges  76 ,  78 . The first composite side edge  76  is formed by the juxtaposition of the tab first side edge  68  and the flap first side edge  72 , while the second composite side edge  78  is similarly formed by the tab second side edge  70  and the flap second side edge  74 . The tab  60  and flap  62  may have substantially the same overall shapes so that the resulting first and second composite side edges  76 ,  78  of each spline tooth  58  are substantially contiguous and smooth, thereby to reduce localized areas of stress and more efficiently transmit torque from the torque transmission component to the clutch plate, or vice versa. 
       FIGS. 4 and 5  show an outer clutch plate  42  in greater detail. The outer clutch plate  42  is substantially similar to the inner clutch plate  38 , except it includes radially outwardly projecting spline teeth  80  configured to slidably engage the grooves formed in the housing  32 . 
     More specifically, the outer clutch plate  42  includes an annular body  82  disposed about an axis  84 . The body  82  includes an inner edge  86  and an outer edge  88 . The spline teeth  80  extend outwardly from the body outer edge  88 . As best shown in  FIG. 5 , each spline tooth  80  may include a tab  90  and a flap  92 . One of the spline teeth  80   a  is shown with an unfolded flap  92  in  FIG. 4 . Accordingly, each spline tooth  80  may have a thickness that is approximately twice that of the body  82 . 
     Any of the spline tooth embodiments discussed above may further include an optional fastener for holding the flap in place against the tab. The fastener may be provided in any of form suitable for securing the flap in the folded position, including, but not limited to, staking, gluing, welding, and riveting. 
     While the foregoing embodiments are described as including a flap that is integrally provided with the tab, it will be appreciated that the flap may be provided as a separate component which is then fastened to the tab. Accordingly, the term “superposed” as used herein and in the claims includes portions of an integral component or two separate components that are folded or otherwise placed adjacent or in contact with one another. 
     The foregoing provides a clutch plate that can advantageously be used in a vehicle transmission or other torque transfer application. The clutch plate includes spline teeth that are reinforced by having a thickness that is larger than that of a body portion, thereby reducing contact stress in the spline teeth. The clutch plates disclosed herein further permit the use of a reduced thickness body portion for a given application, thereby reducing overall clutch plate weight and associated rotating inertia to improve clutch performance. Additionally, the smaller body portion thickness reduces the amount of space required for the torque transmission component in which the clutch plate is used.