Abstract:
A high performance clutch pack for use in the high gear clutch of a POWERGLIDE transmission is disclosed. The present clutch pack is disposed in a modified clutch drum including fluid exhaust vents to reduce piston drag and weight reduction features for accommodating up to ten friction disks and eleven steel disks representing a 150 percent increase in holding force in comparison to the stock POWERGLIDE clutch pack, which typically provides only four friction disks and five steel disks. In one embodiment the steel disks include elliptically shaped holes at predetermined locations for imparting turbulence to the flow of transmission fluid within the clutch pack and also feature anti-drag spacers for reducing parasitic drag during freewheeling. The clutch pack is actuated by a modified clutch piston having an increased stroke correlated to the increased number of friction disks delivering maximum holding force with minimal increase in rotating mass.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. Patent Application No. 10/347,943 now U.S. Pat. No. 6,920,970, which was filed Jan. 21, 2003 entitled HIGH PERFORMANCE CLUTCH PACK FOR TRANSMISSION and claims the benefit thereof under 35 U.S.C. 120. 

   BACKGROUND OF INVENTION 
   The present invention relates to automatic transmission systems and, more particularly, to a high performance clutch pack assembly for a CHEVROLET POWERGLIDE (hereinafter “POWERGLIDE”) automatic transmission. 
   The popularity of the POWERGLIDE automatic transmission dates back to the 1950&#39;s and continues to the present date. Modifications to the stock POWERGLIDE are well known among high-performance and class racing enthusiasts where every advantage is required. It will be appreciated by those skilled in the art that the term “high performance” commonly refers to land vehicle components having enhanced performance characteristics in comparison to the original equipment manufacture (hereinafter “OEM”) specifications. In the context of the present application, the term “high performance POWERGLIDE clutch pack assembly” refers to a clutch pack assembly having a higher torque capacity in comparison to the OEM clutch pack assembly utilized in the POWERGLIDE transmission. 
   Modifications to the clutch pack in the POWERGLIDE are aimed at increasing the so-called holding power of the clutch assembly. For the most part CHEVROLET original equipment manufacture used four friction disks (hereinafter “frictions”) in the OEM high clutch pack. Adding frictions increases the holding power of the clutch pack. The added friction surface area has the same effect as installing a larger diameter clutch in a manual transmission vehicle. Basically, the more power or vehicle weight involved, the larger the friction surface area required. Installing five frictions in the clutch over the stock four increases the friction surface area by 20 percent. Accordingly, installing eight frictions in a POWERGLIDE high clutch that originally had four increases the friction surface area and holding power by 100 percent. 
   The downside to the extra friction surface area is the increase in rotating mass. In the POWERGLIDE the high clutch frictions are spinning at input shaft speed when the transmission is in low gear. Consequently the increased number of frictions can affect performance. 
   Thus, the present invention has been developed to provide substantially increased friction surface area in the POWERGLIDE clutch with minimal increase to the rotating mass of the clutch assembly. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is a high performance clutch pack assembly for a POWERGLIDE transmission including a modified clutch drum for receiving up to ten friction disks and eleven steel disks, which represents a 150% increase in surface contact area and holding force in comparison to the OEM clutch pack assembly having only four friction disks. The present clutch pack assembly also includes a modified clutch hub to accommodate the increased number of friction disks and a modified clutch piston having an increased stroke correlated to the increased number of friction disks and steel disks providing maximum holding force with minimal increase in rotating mass. In one embodiment the steel disks include elliptically shaped holes formed at predetermined locations for imparting turbulence to the flow of automatic transmission fluid (hereinafter “ATF”) within the clutch pack to break the surface tension of the ATF between the friction disks and steel disks. The steel disks also feature anti-drag spacers for reducing parasitic drag between the disks when the clutch is freewheeling (i.e. disengaged). 
   In addition, the present clutch drum is constructed of ductile iron (FCD 600) in comparison to the grey iron (FC 250) used for the OEM clutch drum making it stronger. The present clutch drum is also provided with an array of ATF exhaust vents to reduce drag on the clutch piston and includes weight reduction features to counterbalance the weight of the increased number of disks. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of the present invention are set forth in the appended claims. The invention itself, however, as well as other features and advantages thereof will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures, wherein: 
       FIG. 1A  is a partial cutaway perspective diagram of selected major components of the POWERGLIDE transmission illustrating power flow in low gear; 
       FIG. 1B  is a partial cutaway perspective diagram of selected major components of the POWERGLIDE transmission illustrating power flow in high gear; 
       FIG. 2  is a cross-sectional view of the POWERGLIDE clutch pack assembly of the present invention showing the details of the construction thereof; 
       FIG. 3  is a plan view of a friction disk of the present clutch pack assembly; 
       FIG. 4  is a plan view of a steel disk of the present clutch pack assembly; 
       FIG. 5A  is a cross-sectional view of the OEM clutch drum labeled Prior Art; 
       FIG. 5B  is a cross-sectional view of the modified clutch drum of the present invention; 
       FIG. 6A  is an elevational view of the radial lip seal removed from the clutch piston; 
       FIG. 6B  is an enlarged cross-sectional view of the radial lip seal taken along the section line  6 B— 6 B of  FIG. 6A ; 
       FIG. 7  is a cross-sectional view of present clutch pack assembly installed in its functional position in the POWERGLIDE transmission; 
       FIG. 8  is a cross-sectional view another embodiment of the POWERGLIDE clutch pack assembly of the present invention showing the details of the construction thereof; 
       FIG. 9  is an end view of the clutch drum showing another embodiment of a steel disk of the present invention installed therein; 
       FIG. 10A  is a plan view of another embodiment of a steel disk of the present clutch pack assembly; 
       FIG. 10B  is a side elevational view of the steel disk of  FIG. 10A  shown rotated 90 degrees about its center axis from the position seen in  FIG. 10A ; 
       FIG. 11A  is a left side elevational view of the clutch drum showing the position and orientation of the air vent and ATF exhaust vents; 
       FIG. 11B  is a cross-sectional view of the clutch drum of  FIG. 11A  taken along the section line  11 B— 11 B showing the air vent and ATF exhaust vents therein; and 
       FIG. 12  is a cross-sectional view of an embodiment of a heavy-duty clutch hub of the present invention and shown removed from the clutch pack assembly. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Prior to describing the present invention in detail it may be beneficial to briefly review the major components and basic function of the POWERGLIDE transmission. With reference to the drawings there is shown therein a diagrammatic view of the major components of a CHEVROLET POWERGLIDE transmission, indicated generally at  75  and illustrated in  FIGS. 1A and 1B . The major components thereof are identified and labeled for reference purposes. In stock form the POWERGLIDE is a two-speed automatic transmission. The POWERGLIDE uses two multiple-plate clutches and a brake band to control the planetary gear set. Using these components and various control devices, the transmission  75  provides the following gear positions: Park (P), Reverse (R), Neutral (N), Drive (D), and Low (L). 
   Referring to  FIG. 1A , when the shift lever (not shown) is in low gear, the manual valve in the valve body (not shown) directs pressure to the low servo which applies the low band  15 . The low band  15  holds the high clutch drum  11  and the low sun gear  23  stationary. Because the input shaft  17  from the torque converter  33  is splined to the input sun gear  18  in the rear of the planetary set, indicated generally at  20 , the input sun gear  18  rotates. As can be seen in  FIG. 1A , the long pinions in the planetary set  20  are meshed with the input sun gear  18 . The long pinions  21  are also meshed with the short pinions  22 , which are in turn meshed with the low sun gear  23 . The rotating input sun gear  18  turns the long stationary pinions  21 . Because the clutch drum  11  is being held, the short pinions  22  are forced to “walk” around the low sun gear  23 . This turns the planetary carrier  25 , to which the output shaft  26  is attached. The gear reduction is derived from the difference in the number of teeth on the input sun gear  18  and low sun gears  23 . 
   In high gear, the low band  15  is released and the forward (i.e. high) clutch assembly, indicated generally at  30 , is applied. Because the input shaft  17  is splined to the friction disks in the clutch drum  11  through the clutch hub  12  as shown in  FIG. 1B , the clutch drum  11  turns with the input shaft  17  when the clutch is applied. The low sun gear  23  also turns with the input shaft  17  when the forward clutch assembly  30  is applied. Because the input shaft  17  is splined to the input sun gear  18  in the rear of the planetary carrier  25 , it also is turning with the input shaft  17 . This action effectively locks up the planetary set  20  and the entire planet carrier  25  rotates together. This rotation occurs at the same speed as the input shaft  17  providing a one to one high gear ratio. The high clutch drum  11 , reverse ring gear  28 , and reverse frictions  29  are spinning in high gear. 
   The present invention relates to improvements in the OEM forward clutch pack  63 , clutch piston  10 , the clutch drum  11 , and clutch hub  12 , which will now be described. With reference to  FIG. 2 , there is shown therein an improved POWERGLIDE clutch pack assembly in accordance with the present invention, indicated generally at  100 . In the embodiment shown, the present clutch pack assembly  100  includes a total of ten friction disks  110  and eleven steel disks  105  respectively. It will be noted that installing ten friction disks  110  in the present clutch pack represents a 150% increase in surface contact area and holding force in comparison to the standard POWERGLIDE clutch pack having four friction disks. 
   Referring now to  FIG. 3  each friction disk  110  is comprised of a core member  102  fabricated from steel or other material suitable for this purpose. Core members  102  include an internal spline  103  formed on the inside diameter thereof for mating engagement with the external spline  115   a  formed on the outside diameter of the clutch hub  115  ( FIG. 2 ). Each core member  102  is provided with a die cut layer of friction material as at  104  and also on the opposite surface thereof, which is secured to the core member  102  by a suitable adhesive such as thermosetting resin. 
   In the preferred embodiment a frictional material such as WPC PREMIUM RED™, ALTO RED EAGLE™, RAYBESTOS BLUE PLATE SPECIAL™ or other frictional material having physical and chemical properties suitable for this application is provided. 
   A steel disk  105  (hereinafter “steel(s)”) is illustrated in  FIG. 4 . In the preferred embodiment steel  105  includes a body member  112  having twelve anti-rotation tabs  112   a  formed thereon and projecting radially outward therefrom. Anti-rotation tabs  112   a  are designed for sliding engagement with a mating pattern of twelve axial grooves  116  formed in the interior wall of the clutch drum, indicated generally at  120 , as most clearly shown in  FIG. 5 . It will be appreciated that although anti-rotation tabs  112   a  prevent rotation, steels  105  are capable of axial movement within the grooves  116  or  116 ′ formed in the clutch drum  120  during operation as hereinafter explained. 
   It will be appreciated that the increased number of frictions  110  and steels  105  and the corresponding increased length of the clutch pack assembly  100  requires modification of the present clutch drum  120 , the clutch hub  115 , and the clutch piston assembly, indicated generally at  130 , as shown more clearly in  FIGS. 5A and 5B . In the present invention the axial length of grooves  116 ,  116 ′ defined by dimension “X” in  FIG. 5B  has been increased in comparison to the OEM clutch drum to accommodate the increased number of frictions  110  and steels  105 . 
   Accordingly, the length of the piston bore defined by dimension “Y” in  FIG. 5B  is decreased in comparison to the OEM clutch drum  11  ( FIG. 5A ). However, the operating stroke of the piston  125  has been increased to accommodate the increased number of frictions  110  and steels  105  as explained hereinafter in further detail. 
   The clutch drum  120  has also been modified in comparison to the OEM design to include weight-reducing means formed therein to compensate for the added weight resulting from the increased number of frictions  110  and steels  105  in the clutch pack assembly  100 . Such weight-reducing means include, but are not limited to, the following structures. In the preferred embodiment the present clutch drum  120  is provided with a secondary pattern of twelve grooves  116 ′ machined in parallel, spaced apart relation at a position rotated 15 degrees about the center axis and intermediate the primary pattern of grooves  116 . The secondary grooves  116 ′ are identical in all aspects to the primary grooves  116 . Thus, it will be understood that either pattern of grooves  116 ,  116 ′ may receive the steels  105  in sliding engagement during assembly of the present clutch pack  100 . 
   The increased length of the clutch pack  100  also requires a corresponding increase in the axial length of the spline  115   a  on the clutch hub  115  whereon the friction disks  110  are slidingly engaged. In the preferred embodiment the spline  115   a  of the present clutch hub  115  has been lengthened approximately 0.150″ in comparison to the OEM design. The design of the present clutch hub  115  also provides weight-reducing means including, but not limited to, the following structures. Clutch hub  115  includes a plurality of weight-reducing holes  117  formed within the radial web  115   c  of the hub  115  at predetermined locations to compensate for the increased axial length of the spline  115   a  and the corresponding weight increase of the hub  115 . 
   Further, the present clutch hub  115  is constructed from a steel forging in accordance with AISI 1045, which is significantly stronger than the OEM hub casting. 
   The increased number of frictions  110  and steels  105  also requires modification of the clutch piston  125  including a reduction in the overall axial length as at dimension “H” ( FIG. 2 ) in comparison to the OEM design. However, the operating stroke of the piston  125  has been increased to compensate for the increased number of frictions  110 , which require 0.008–0.010″ clearance therebetween when the clutch is disengaged and the frictions  110  rotate freely within the modified clutch pack. 
   The present piston  125  also includes a primarily radial lip seal  126  as shown in  FIGS. 6A and 6B . As most clearly shown in  FIG. 6B , the lip seal  126  includes a core member  126   a  which is generally rectangular in cross-section that is integrally formed with an outwardly angled lip portion  126   b . The lip seal  126  is installed in a modified groove  133  formed about the peripheral, leading edge of the clutch piston  125  to affect a seal within the piston chamber  145  as shown in  FIG. 2 . In the preferred embodiment lip seal  126  is fabricated from fluorocarbon rubber material in the 90 durometer range. A secondary lip seal  126 ′ of substantially similar construction is installed within groove  131  formed in the drum  120  to seal the inner surface of the piston  125  ( FIG. 2 ). 
   The present clutch piston  125  is fabricated from a high-grade aluminum material such as AISI 2014-T6 or AISI 7075-T6 forging or billet in comparison to the OEM die cast piston. 
   In an assembly procedure of the present clutch pack assembly  100 , the piston  125  including radial lip seal  126  as shown in  FIG. 2  is initially inserted in the clutch drum  120  with lip seal  126 ′ preinstalled thereon. Next, the compression springs  127  are positioned on spring guides  125   a  and the spring retainer  128  is installed being secured in position by retaining ring  129  as shown in  FIG. 2 . 
   Next, the frictions  110  and steels  105  are arranged alternately within the drum  120  in the following manner: piston, steel, friction, steel, friction, steel, friction, steel, friction, steel, friction, steel, friction, steel, friction, steel, friction, steel, friction, steel, friction, steel, pressure plate such that all of the frictions  110  slidingly engage the spline  115   a  on the clutch hub  115 . It will be appreciated that frictions  110  and steels  105  are arranged such that adequate clearance is maintained therebetween to permit proper operation without excessive wear. Next, the pressure plate  135  is installed and held in position by retaining ring  132 . 
   Thereafter, the clutch assembly is ready for installation in its functional position on the mating spline  140   a  of the input shaft  140 , which engages the internal spline  115   b  on the clutch hub  115  within the transmission as shown in  FIG. 7 . 
   In normal operation when the POWERGLIDE is in low gear, the low band  15  (refer to  FIG. 1A ) is applied to the outside diameter of the clutch drum  11  and the drum is held stationary. The clutch piston  125  is biased to the low gear position (i.e. piston displaced to bottom of its travel in piston bore) as shown in  FIG. 2  and the frictions  110  spin freely within the clutch pack assembly  100  with the rotation of the input shaft  17 . 
   In high gear ATF flows to the inlet ports  142  under increased pressure and enters piston chamber  145 . In response to ATF pressure, the clutch piston  125  is stroked in the aft direction against the force of springs  127  compressing the steels  105  and frictions  110  axially against the pressure plate  135  to apply the high clutch. In this position the clutch drum  120  turns with the input shaft providing a one-to-one high gear ratio. 
   Referring now to  FIG. 8  there is shown therein another embodiment of the present invention including further improvements to the clutch pack assembly, indicated generally at  100 ′, the clutch hub  115 ′, and also to the clutch drum  120 ′. In this embodiment the clutch pack assembly  100 ′ includes a plurality of steels  105 ′ (i.e. up to eleven total) each having a body member  112 ′ having twenty-four anti-rotation tabs  112   a ′ projecting radially outward to slidingly engage the drum  120 ′ as more clearly shown in  FIG. 9 . 
   Anti-rotation tabs  112   a ′ are designed to engage the mating array of primary axial grooves  116  and the mating array of secondary axial grooves  116 ′ formed intermediate the primary axial grooves simultaneously. Anti-rotation tabs  112   a ′ permit axial movement within the grooves  116 ,  116 ′, but prevent rotation of the steels  105 ′ within the drum  120 ′. Thus, in operation the torque applied to steels  105 ′ upon clutch engagement is transferred to the flank surfaces of twenty-four tabs  112   a ′ in comparison to the twelve tabs  112   a  of the steels  105  in the previous embodiment ( FIG. 4 ). The distribution of torque onto twenty-four steels  105 ′ results in significantly less mechanical wear (i.e. notching) on the steels at their interface with grooves  116 ,  116 ′ and provides a clutch pack  100 ′ having substantially increased service longevity. 
   Referring to  FIGS. 10A and 10B  another embodiment of a steel disk, indicated generally at  105 ″, is illustrated. It can be seen that the body  112 ″ of each steel  105 ″ includes a plurality of so-called TURBULATOR holes  160  formed therein at predetermined locations. TURBULATOR steel disks  105 ″ of the type sold under the tradename POWERGLIDE TURBULATOR KOLENE® and marketed by ALTO Products Corporation, Artmore, Ala. 36504 are suitable for this purpose. TURBULATOR holes  160  reduce heat and parasitic drag by introducing turbulence to the flow of ATF as it passes through the elliptically shaped holes  160  formed within each of the steels  105 ″ thereby breaking the surface tension of the ATF between the frictions  110  and steels  105 ″. Such TURBULATOR technology is known in the prior art having been developed to give positive, aggressive shift points, shorter shift times, and consistent shift quality over the life of the clutch pack. 
   However, the present steel disks  105 ″ including the TURBULATOR technology in combination with the array of twenty-four anti-rotation tabs  112   a ′ were developed by ALTO Products Corporation at the request of the applicant herein for the present POWERGLIDE clutch pack since such steels  105 ″ (as illustrated in  FIG. 10A ) were heretofore unknown in the prior art. 
   Still referring to  FIGS. 10A and 10B  steels  105 ″ are each provided with a plurality of spacers  165  fabricated from Viton® or another heat-resistant rubber material suitable for this purpose. Spacers  165  are slightly thicker than the frictions  110  used in the clutch pack separating the steels  105 ″ from the frictions  110  and functioning to eliminate the parasitic drag therebetween, which occurs whenever the clutch is disengaged. Steels having such spacers  165  are known in the prior art being manufactured by ALTO Products under the tradename ANTI-DRAG™ plates. However, such ANTI-DRAG™ plates in combination with the array of twenty-four tabs  112   a ′ were developed by ALTO Products Corporation at the request of the applicant for the present POWERGLIDE clutch pack since such steels  105 ″ (as illustrated in  FIG. 10A ) were heretofore unknown in the prior art. 
   Referring to  FIGS. 11A and 11B  it can be seen that in this embodiment the clutch drum  120 ′ is provided with a plurality of ATF exhaust vents, indicated generally at  150 , that are positioned at regular intervals in fluid communication with the piston chamber  145  and drilled axially through the end face  120   a ′ of drum  120 ′ to the exterior thereof. Vents  150  function to rapidly exhaust ATF from the piston chamber  145  to reduce drag on the piston  125  and hasten its engagement during the apply cycle of the clutch. 
   This embodiment also includes an air vent, indicated generally at  180 , including an air passage  182  wherein a check ball  185  is permanently captured. When the clutch is applied, the clutch drum  120  revolves at high speed with the input shaft  140  ( FIG. 7 ) and check ball  185  is unseated by centrifugal force opening air passage  182 . Thus, air vent  180  functions to evacuate air from the piston chamber  145  during clutch engagement. 
   As most clearly shown in  FIG. 11A  the end face  120   a ′ of the clutch drum  120 ′ in this embodiment is also machined to provide a counterbore as at  170  to receive a thrust bearing  175  ( FIG. 8 ) therein. A thrust bearing  175  such as a Torrington® radial roller bearing having a plurality of radially disposed roller elements (not shown) is used to distribute the axial load in this application in lieu of an OEM thrust washer. Such thrust bearings are manufactured to industry specifications and carry a dynamic load rating, which typically increases with the nominal outside diameter of the thrust bearing  175 . 
   For this embodiment a heavy-duty version of the present clutch hub  115 ′ is fabricated from a hardened chrome molybdenum steel alloy (Chromoly) as shown in  FIG. 12 . It can be seen that in this heavy-duty version the weight-reducing holes  117  formed within the radial web  115   c  of the previous clutch hub  115  ( FIG. 2 ) have been omitted from the radial web  115   c ′ of the clutch hub  115 ′ ( FIG. 12 ) to provide additional strength. In this embodiment the external spline  115   a ′ of the present clutch hub  115 ′ has also been lengthened approximately 0.150″ in comparison to the OEM design to accommodate the increased number (i.e. up to ten) of frictions  110  and (i.e. up to eleven) steels  112 ′ or  112 ″. 
   In summary, it can be seen that the present invention provides a high performance clutch pack assembly for a POWERGLIDE transmission including an increased number of friction disks and steel disks, which provides substantially more friction surface area and increased clutch holding power without compromising performance. 
   Although not specifically illustrated in the drawings, it should be understood that additional equipment and structural components will be provided as necessary and that all of the components described above are arranged and supported in an appropriate fashion to form a complete and operative high performance clutch pack assembly for a Powerglide transmission incorporating features of the present invention. 
   Moreover, although illustrative embodiments of the invention have been described, a latitude of modification, change, and substitution is intended in the foregoing disclosure, and in certain instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of invention.