Abstract:
Friction clutch reaction plate assemblies include two thin reaction plates which are preferably secured together in spaced relation to form a single reaction plate assembly. At least plate includes through openings which improve fluid flow between and around the plates and both plates include projections which align and define the spacing between the plates. The two plates may be secured together by various means such as spot welding, CD welding, laser welding, riveting or an adhesive. The axial space between the splines or teeth which couple the reaction plate to a clutch component (either a hub or a housing) may be reinforced with material to improve surface area contact. The reaction plate assembly has a thickness substantially equal to a conventional reaction plate in order that it may be readily substituted into current friction clutch assemblies.

Description:
FIELD 
       [0001]    The present disclosure relates to reaction plates for friction clutch assemblies and more particularly to two piece reaction plates for friction clutch assemblies. 
       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]    Friction clutches, also referred to as friction clutch packs or friction clutch assemblies, are widely used in modern motor vehicle automatic transmissions. Friction clutches provide a modulatable torque transmitting device between two members rotating at different speeds or a rotating member and a stationary structure in which case the device is generally referred to as a brake. Such friction clutches and brakes comprise first and second interleaved pluralities of discs or plates that are coupled to respective first and second members, such as an input shaft and an output shaft or fixed member, and an actuator that compresses the plates or discs, thereby transmitting torque through the device. 
         [0004]    The plates or discs are of two types: friction plates or discs are relatively thin metal and include bands or annuli of friction material on both surfaces. These friction plates or discs are interleaved with metal reaction plates which are thicker and do not include such friction material. All of the friction plates are coupled to, for example, an input member by splines and all of the reaction plates are coupled to, for example, an output member, also by splines. 
         [0005]    As clutch torque throughput and heat dissipation requirements have increased on modern motor vehicle transmissions, so has the thickness of the clutch plates, particularly the reaction plates. Such thickness increases increase the mass and rotational inertia of such plates and of the overall transmission, thereby reducing the efficiency of the transmission and the fuel economy of the powertrain and vehicle. 
         [0006]    It would therefore be desirable to reduce the mass of such reaction plates without compromising the function and heat transfer characteristics of thicker and more massive reaction plates. The present invention is so directed. 
       SUMMARY 
       [0007]    The present invention provides friction clutch reaction plate assemblies comprising two thin reaction plates which are preferably secured together to form a single reaction plate assembly. One or both plates include through axial openings which improve fluid flow in and around the plates and both plates include projections which align and establish the spacing between the plates. The two plates may be secured together by various means such as spot welding, CD welding, laser welding, rivets or an adhesive. The reaction plate assembly has a thickness substantially equal to a conventional, solid reaction plate in order that it may be readily substituted into current friction clutch designs. The axial space between the splines or teeth which couple the reaction plate to a clutch component (either a hub or a housing) may be filled or reinforced with plastic or epoxy to improve surface area contact. The space between the plates allows fluid flow there-between and provides improved heat transfer and thus improved reliability and service life. 
         [0008]    Thus it is an aspect of the present invention to provide a friction clutch reaction plate assembly of conventional thickness which is assembled from two thin plates which define an annular space there-between. 
         [0009]    It is a further aspect of the present invention to provide a friction clutch reaction plate assembly fabricated of two spaced apart reaction plates which are secured together. 
         [0010]    It is a still further aspect of the present invention to provide a friction clutch reaction plate assembly fabricated of two spaced apart reaction plates which are secured together by spot welding, CD welding, laser welding, rivets or an adhesive. 
         [0011]    It is a still further aspect of the present invention to provide a friction clutch reaction plate assembly fabricated of two spaced apart reaction plates one or both of which has axial openings which improve fluid flow in and around the plates. 
         [0012]    It is a still further aspect of the present invention to provide a friction clutch reaction plate assembly fabricated of two spaced apart reaction plates one or both of which has axial projections which establish the spacing between the plates. 
         [0013]    It is a still further aspect of the present invention to provide a friction clutch reaction plate assembly fabricated of two spaced apart reaction plates having a plastic or epoxy filler between the splines or teeth of the assembled reaction plate. 
         [0014]    Further aspects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0015]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0016]      FIG. 1  is a sectional view of a friction plate clutch assembly incorporating the present invention; 
           [0017]      FIG. 2  is a fragmentary perspective view of a two piece reaction plate assembly according to the present invention; 
           [0018]      FIG. 3  is a full sectional view of a two piece reaction plate assembly according to the present invention taken along line  3 - 3  of  FIG. 2 , in pre-assembly configuration; and, 
           [0019]      FIG. 4  is a fragmentary perspective view of a two piece reaction plate assembly according to the present invention illustrating the securement means and the material filler disposed between the teeth or splines. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0021]    With reference to  FIG. 1 , an exemplary friction clutch assembly is illustrated and generally designated by the reference number  10 . The friction clutch assembly  10  may be a component of, for example an automatic transmission, a transfer case or other power and torque controlling and transmitting device. The friction clutch assembly  10  is disposed between a rotating hub  12  having a set of axially extending male splines  14 . The hub  10  includes a radially and circumferentially extending flange  16  which may be connected to a rotating shaft, quill or a member of another clutch or brake (all not illustrated). A plurality of friction plates or discs  20  having female splines  22  about their inner edges are complementary to the male splines  14  on the hub  12 . The female splines  22  engage the male splines  14  on the hub  12  and thus the plurality of friction plates or discs  20  rotate with the hub  12 . Each face of the plurality of friction plates or discs  20  includes a band or annulus of friction material  24  which is secured thereto by an adhesive or in a similar manner. 
         [0022]    Interleaved with the plurality of friction plates or discs  20  is a plurality of reaction plate assemblies  30 . The reaction plate assemblies  30  include male splines  32  about their outer peripheries and may be fabricated of either steel or aluminum. As will be described in more detail below, each of the plurality of reaction plate assemblies  30  includes a first reaction plate  34 A and a second reaction plate  34 B separated by an annular space  36 . The male splines  32  are complementary to and engage female splines  38  extending axially along an inner surface of a housing  40  or other structure. 
         [0023]    At one end of the friction clutch assembly  10 , the housing  40  includes an inwardly extending web of flange  42  terminating in a radially extending surface  44  that acts as a stop for a circular backing plate  46 . At the opposite end of the friction clutch assembly  10  is disposed an apply plate  48  which is acted upon by a piston or an actuator member  52  of a hydraulic, electric or pneumatic actuator or operator  54 . In accordance with conventional practice, when the actuator or operator  54  is energized, the piston or actuator member  52  extends, applies pressure to and translates the apply plate  46  which, in turn, applies pressure to the pluralities of friction plates  20  and reaction plates  30 , thereby frictionally connecting and, if a speed difference exists, transferring torque between the hub  12  and the housing  40 . It should be appreciated that the foregoing description is illustrative only and that variations such as a fixed or stationary hub  12  and rotating housing  40  as well as friction plates  20  splined to the outer housing  40  and reaction plates  30  splined to the inner hub  12  are all within the purview of the present invention. 
         [0024]    Referring now to  FIGS. 2, 3 and 4 , the first reaction plate  34 A and the second reaction plate  34 B are both preferably approximately 0.8 mm. (0.0315 in.) thick and the annular space  36  there-between is also approximately 0.8 mm. for a total thickness of approximately 2.4 mm. (0.0945 in.). This thickness (2.4 mm.) is a typical thickness for a conventional (solid) reaction plate and thus the reaction plate assembly  30  according to the present invention may readily replace conventional reaction plates without modification to the friction clutch assembly while enjoying a mass reduction of approximately 33%. It should be understood, however, that both the plate thickness and the ratio of the plate and space thicknesses may be varied to accommodate and satisfy various applications without departing from the scope of this invention. 
         [0025]    Each of the first reaction plates  34 A and the second reaction plates  34 B includes a plurality of male splines  32  about their peripheries. Each of the first reaction plates  34 A and the second reaction plates  34 B also preferably includes a plurality of spaced apart through oil and/or air openings  62  arrayed in a circle disposed approximately in the middle of the reaction plates  34 A and  34 B. While the number of openings  62  will vary depending upon their size and the size of the reaction plates  34 A and  34 B, it has been found that between twelve and thirty openings  62  has proven functional with between twenty and twenty-six openings  62  being preferred. The through openings  62  allow oil to pass in and out of the friction interfaces and the annular space  36  between the plates  34 A and  34 B. The through openings  62  also allow air to enter the friction interfaces when the friction clutch assembly  10  is released, thereby more quickly reducing drag. 
         [0026]    Each of the first reaction plates  34 A further includes a plurality of upset or partially pierced openings which create recesses  66  on the outer surfaces of the reaction plates  34 A and a first plurality of pads, lugs or projections  68 A on the inner surface which extend half way across the annular space  36  and contact a second and like plurality of correspondingly located pads, lugs or projections  68 B on the inner surfaces of each of the second reaction plates  34 B. The second plurality of lugs or projections  68 B likewise extend half way across the annular space  36  and are also upset or partially pierced openings which create recesses  66  on the outer surfaces of the second reaction plates  34 B and the lugs or projections  68 B on the inner surfaces. With reference to the width (0.8 mm.) of the annular space  36  given in the example above, each of the lugs or projections  68 A and  68 B has a height of 0.4 mm. (0.0157 in.). 
         [0027]    The lugs or projections  68 A and  68 B establish the desired spacing between the first reaction plates  34 A and the second reaction plates  34 B. Accordingly, they are preferably formed in a die with blind holes having flat bottoms in order that they have both accurately flat end surfaces and heights. Alternatively, after being formed by, for example, piercing or upsetting, the end surfaces of the lugs or projections  68 A and  68 B may be finished by grinding. 
         [0028]    The plurality of partially pierced openings forming the recesses  66  and the lugs or projections  68 A and  68 B are preferably arrayed in inner circles designated by a dashed line  70 A adjacent the inner edge of the reaction plates  34 A and  34 B, intermediate circles designated by a dashed line  70 B where they alternate with the through openings  62  and outer circles designated by a dashed line  70 C which passes generally through the splines  32 . The recesses  66 , best illustrated in  FIG. 4 , created by the partial piercing are beneficial as they reduce spin losses by allowing air to be introduced into the friction interfaces when the friction clutch assembly  10  is released. 
         [0029]    Referring now to  FIGS. 3 and 4 , the first reaction plate  34 A is placed adjacent the second reaction plate  34 B with the lugs or projections  68 A of the first reaction plate  34 A facing or extending toward, and aligning with, the lugs or projections  68 B on the second reaction plate  34 B and the splines  32  on each of the plates  34 A and  34 B axially aligned. So arranged, the reaction plate assemblies  30  may be installed within a friction clutch such as the friction clutch assembly  10 . For various applications, however, it may be desirable to secure the first reaction plates  34 A to respective second reaction plates  34 B. This may be readily accomplished by spot welding, laser welding or discharge (CD) welding, preferably at a certain number of the recesses  66 A (and the lugs or projections  68 A and  68 B) spaced about the plates  34 A and  34 B. Alternatively, other welding techniques or adhesive bonding may be utilized. As a further alternative, the plates  34 A and  34 B may be riveted together with either separate rivets or parent material rivets also illustrated at  66 A. 
         [0030]    Referring now to  FIG. 4 , in order to achieve optimum spline contact area, it may be desirable to fill the space between the splines  32  of the reaction plates  34 A and  34 B with a plastic or epoxy material  72 . Alternatively, one or both of the reaction plates  34 A and  34 B may be stamped or extruded in the region of the splines  32  to allow for full metal thickness at the splines  32 , i.e., 2.4 mm. in the example given above, again to improve spline contact area. Finally, with reaction plate assemblies  30  having welded or otherwise secured plates  34 A and  34 B, it may be desirable to re-stamp the splines  32  to ensure optimum and uniform surface contact with a mating housing such as the outer housing  40 . 
         [0031]    Thus it will be appreciated that a friction clutch assembly  10  incorporating reaction plate assemblies  30  according to the present invention achieves a reaction plate mass reduction of approximately 33%, may have reaction plates of steel or aluminum, has lower inertia, better cooling, lower spin losses and achieves improved air and oil flow through the clutch as discussed above. 
         [0032]    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.