Abstract:
Segmented steel core plates for either double sided or single sided wet clutch friction plates or separator plates and a process for making the same are disclosed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. provisional patent application Ser. No. 60/775,492 filed on Feb. 21, 2006. 

   The present invention relates to segmented steel core plates for either double sided or single sided wet clutch friction plates or separator plates and a process for making the same. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to steel core plates or discs which are used in multi-plate wet clutch packs for automatic transmissions or transfer cases for vehicles or other friction clutch applications where an annular core plate is segmented with interlocking end portions to form an annular ring. Annular friction rings or discs are conventionally used in wet clutch packs of interleaved clutch plates that are alternately connected to an inner hub and an outer drum of a clutch assembly. The clutch plates are engaged to rotate the parts of the clutch assembly together by a hydraulically or spring-actuated piston. A friction plate or disc normally consists of an annular steel ring or plate, which serves as a core plate and a pair of annular friction facings that are riveted or otherwise secured to the core plate to complete the friction disc. 
   In the manufacturing process, blanking out of friction rings and annular core plates produces considerable waste. The U.S. Pat. No. 4,260,047 to Nels use an annular core plate and segmented friction facings having tab and slot interlocking ends. The friction facings consist of quarter circle segments which are blanked out of a rectangular sheet of friction material that is formed with a plurality of parallel grooves, with the tabs and slots formed in ungrooved portions. The segments are interconnected to form a ring and are bonded to the core plate. 
   The Mannino, Jr., U.S. Pat. No. 4,674,616 patent, owned by the common assignee herein, relates to a friction disc with a segmented core and segmented facings. In the Mannino patent, the core plate has a plurality of arcuate segments with tab and slot end portions which interlock to form an annular core plate. The friction facings are also formed of arcuate segments that overlap the interlocking end portions of the core plate and are suitably bonded thereto on both faces. The facing segments do not need to be interconnected together and the bonding of the friction segments to the interlock core plate segments in an overlapping manner prevents disassembly of the core plate. Both the interlocking core plate segments and friction facing segments are perforated to permit use of alignment pins for handling orientation and alignment of the segments for assembly and bonding. 
   Although these and other similar methods reduce the waste friction material, the multi-step manufacturing processes and waste of material in blanking out the core plate remains. The present invention provides improvements on these plates and processes for making the plates. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present invention relates to an annular core plate which is segmented with interlocking end portions to form a ring. In certain embodiments, the core plate or friction disc comprises “prime” segments, i.e. where the number of spline teeth is divisible by 3 segments. In other embodiments, the friction disc comprises “non-prime” segments, i.e., where the number of spline teeth is not evenly divisible by 3 segments. Two or more of these segmented steel core plates, formed either with the prime or non-prime segments, are joined together to form what is generally called a “stack” or “clutch pack” in the industry. 
   In another embodiment, one or more of the prime or non-prime segments are missing from an annular ring in a stack that contains three or more annular rings that channels are formed through the stack to allow oil to flow through the clutch pack. 
   In yet another embodiment, openings are stamped, or formed, into the segments that are stacked or laminated together. The openings intersect circumferentially and create offset radial channels or openings into opposite edges of the segment to form oil passages into the plate or disc. 
   The present invention increases the efficiency of manufacturing steel core plates and separator plates by reducing the amount of scrap material from the manufacturing process. 
   In another aspect of the present invention provides a method for making segments and assembly of the segments into a single ply or thickness core plate. 
   Other objects and advantages of the present invention will become apparent to those skilled in the art upon a review of the following detailed description of the preferred embodiments and the accompanying drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a plan view of a friction disc comprising “prime” segments, i.e. where the number of spline teeth is divisible by 3 segments. 
       FIG. 1B  is a plan schematic view of a blanking process for segments where segments are punched. 
       FIG. 2A  is a plan view of a friction disc comprising “prime” segments, i.e., where the number of spline teeth is not evenly divisible by 3 or 5 segments. 
       FIG. 2B  is a plan schematic view of a blanking process for “non-prime” segments where different segment punches are activated to allow for the “odd” segment. 
       FIG. 3A  is a plan view, partially in phantom, of a friction discs having “non-prime” segments. 
       FIG. 3B  is a schematic plan view showing a process for stamping “non-prime” segments and further stamping tab lock perforations. 
       FIG. 3C  is a cross sectional view showing a semi-perforation in a first segment and in a second segment. 
       FIG. 4  is a schematic plan view of a die layout for segmenting and lamenting steel core plates. 
       FIGS. 5A-F  is schematic illustrations of different joint designs that are useful in connecting segments of the core plate. 
       FIGS. 6A ,  6 B and  6 C show the laminated riveted core plate:  FIG. 6A  is a plan view,  FIG. 6B  is a partial cross section, and  FIG. 6C  is an exploded cross sectional view taken from  FIG. 6B . 
       FIG. 7  is a plan view of a stock of core plates formed of multiple segments. 
       FIG. 8  is a side elevation view of the core plate of  FIG. 7 . 
       FIG. 9  is a plan view of a friction disk having a plurality of stocked core plates. 
       FIG. 10  is a side elevation view of the friction disk of  FIG. 9 . 
       FIG. 11   a  is a front elevation view of a core plate of the present invention. 
       FIG. 11   b  is a front elevation view of the core plate of  FIG. 11   a  with a friction material applied to the core plate. 
       FIG. 11   c  is a side elevation view of the core plate of  FIG. 11   b.    
       FIG. 12  is a front elevation view of a core plate with additional features for securing the segments together. 
       FIG. 13  is a front elevation view of a core plate with additional features for securing the segments together. 
   

   DESCRIPTION OF THE INVENTION 
   The present invention is useful for both producing core plates having either prime or non-prime number of spine teeth on the core plates. According to the present invention, the segments are considered “prime” if the number of spine teeth on the disc is divisible by three or five segments. 
     FIG. 1A  shows a multi-plate clutch pack  10  for an automatic transmission or for other suitable clutch plate applications. The multi-plate clutch pack  10  includes a plurality of plates. For ease of explanation, one plate will be discussed in detail. The core plate  11  has a plurality of teeth  12 . The teeth  12  may be on either the inner or outer periphery of the plate  11 . The core plate  11  is comprised of three identical arcuate segments  13 . Each segment  13  has a tab  14  and a slot  15  at opposing ends of the segment. The tab  14  and the slot  15  at either end are complimentary to and conformably receiving a tab  14  in a slot  15  in the next adjacent segment. It is to be understood that other shapes of tab and slot arrangements are useful with the present invention and such various combinations are shown in  FIGS. 7A  thru  7 F herein. In the embodiment shown in  FIG. 1A , the segmented core plate has 45 teeth, which is evenly divisible by 3. Thus, the segments  13  are identical in shape. 
     FIG. 1B  shows identical segments  13  which are stamped from a suitable sheet of steel  8 . The sheet has guide holes  9  for guiding the sheet  8  through a suitable stamping device (not shown). In such stamping operation, the stamping and/or punch out for segmenting and laminating steel core plates can be done in any suitable manner. The materials are then advanced to a knockout station. 
     FIG. 2A  discloses a friction disc or clutch plate  20  which may be utilized in a multi-plate clutch pack for an automatic transmission or for other suitable clutch plate applications. The friction disc  20  includes a steel core plate  21  having a plurality of teeth  22 . The teeth  22  may be on either the inner or outer periphery of the plate  21 . The core plate  21  is comprised of three arcuate segments  23 . Each segment  23  has a tab  24  and a slot  25  at opposing ends of the segment. The tab  24  and the slot  25  at either end are complimentary to and conformably receiving a tab  24  in a slot  25  in the next adjacent segment. It is to be understood that other shapes of tab and slot arrangements are useful with the present invention and such various combinations are shown in  FIGS. 7A  thru  7 F herein. 
   In the embodiment shown in  FIG. 2A , the segmented core plate  21  has 41 teeth, which number is not evenly divisible by 3 or 5. Thus, the core plate  21  is referred to as “non-prime” since number of teeth, 41, is not evenly divisible by 3 or 5. The non-prime core plate  21  includes a first segment  23 A, a second segment  23 A′ which is identical to the first segment  23 A, and a third segment  23 B which is different from the first and second segments  23 A and  23 A′. Also,  FIG. 2A  shows the arcuate length of each segment where segments  23 A and  23 A′ have an arcuate measurement or length that is slightly less than the accurate measurement or length of the third segment  23 B. 
     FIG. 2B  is a schematic illustration of a steel sheet  28  which is stamped with identical segments  23 A and  23 A′ and with different segment  23 B. The sheet has guide holes  29  for guiding the sheet  28  through a suitable stamping device (which will be generally described later in this document). In such stamping operation, the stamping and/or punch out for segmenting and laminating steel core plates can be done in any suitable manner. The materials are then advanced to a knockout station to remove the completed core plates from the stamping operation. 
   In certain aspects of the invention, cam activated assemblies are used for the different shaped segment to allow for the segments of different size. For example, a first punch (not shown) is cycled for 2 press strokes to first punch out an A segment and then an A′ segment. Thereafter, a second punch (not shown) is activated for one stroke to punch the B segment. When the first cam punch is engaged, the second cam punch is released and does not punch. According to one method of the present invention, a pad blanking processing can be used where the segment is pushed back into the strip. A knockout station, not shown, is used to punch out both the A and B segments. 
   The present invention relates to non-prime segments formed into a steel core plate which are then laminated together to form a stack.  FIG. 3A  is a schematic illustration showing core plates interlocked together. 
   In  FIG. 3A , a multi-plate clutch pack  30  for an automatic transmission or for any other suitable clutch plate application is shown. The multi-plate clutch pack  30  includes a plurality of core plates. For ease of explanation, two adjacent core plates will be discussed in detail. As such these two core plates will be referred to as either the first, or upper, core plate  31  and the second, or underlying, core plate  31 ′. As shown in  FIG. 3A , the first core plate  31  has teeth  32  on the inner periphery thereof. Again, it should be understood that the core plates  31  and  31 ′ may have teeth on an outer periphery (not shown). 
   In certain embodiments, one or more openings can be provided in each segment to receive alignment pins (no shown) for purposes of assembly. When the tabs and slots of the segments are interlocked, an annular plate or ring is formed. 
   In the embodiment shown in  FIG. 3A , the core plate  31  is formed of three arcuate segments: first and second identical segments  33 A and  33 A′, and a third, different, segment  33 B. The segments  33 A,  33 A′ and  33 B each have a tab  34  and an adjacent slot  35  at each end of the segment. The tab  34  and the slot  35  are complimentary to and conformably receiving an adjacent tab  34  and an adjacent slot  35  on adjacent, and opposing, segments. When the tabs  34  and slots  35  of the segments  33 A,  33 A′ and  33 B are interlocked, the annular core plate  31  is formed. 
     FIG. 3A  shows, in phantom, a second core plate  31 ′ behind, and in coaxial alignment with, the first core plate  31 . The second core plate  31 ′ is circumferentially rotated with respect to the first core plate  31  such that the interlocking tabs and slots  34  and  35  on the first core plate  30  are circumferentially displaced with respect to interlocking tabs  34 ′ and slots  35 ′ on the second core plate  31 ′. In certain embodiments, the underlying core plate  31 ′ is circumferentially rotated approximately 60° such that the second set of interlocking tabs and slots  34 ′ and  35 ′ are approximately 60° from the first interlocking tabs and slots  34  and  35 . 
   As shown in  FIGS. 3A ,  3 B, and  3 C, the segments  33 A,  33 A′ and  33 B of the first core plate  31  can contain a predetermined number of perforations  36 . The perforations axially extend through the core plate and can be generally equidistantly spaced apart from adjacent perforations. It is to be understood that, in various embodiments, each segment can have any predetermined desired number of perforations. In the embodiment shown, each segment  33 A,  33 A′ and  33 B has four perforations labeled  36 A,  36 B,  36 C, and  36 D. 
   The first, second and third segments  33 ′A,  33 ′A′ and  33 ′B of the second, or underlying, core plate  31 ′ contain a plurality of projections  38  for engagement or locking, with adjacent perforations  36  in the first core plate  31 . As shown in  FIGS. 3A ,  3 B, and  3 C, the segments  33 ′A,  33 ′A′ and  33 ′B can contain a predetermined number of projections  38 . It is to be understood that each segment can have any predetermined desired number of semi-perforations  38 . In the embodiment shown, each segment  33 ′A,  33 ′A′ and  33 ′B has four projections labeled  38 A,  38 B,  38 C, and  38 D.  FIG. 3C  shows a schematic illustration of one projection  38  which is used to lock the first core plate  31  to the adjacent core plate  31 ′. The perforation  36  has the projection  38  extending within the perforation  36 . The perforation  36  can have any desired shape that will accommodate any desired shape of projection  38 . 
   It should be noted that core plates  31 ,  31 ′ and any additional core plates comprising the stack  30  can be further strengthened by using suitable processes. For example, an acid etch and glue process can be used. In other manufacturing embodiments, the layers of core plates can also be welded together, using, for example, resistance laser welding or capacitor welding discharge or the like processes. As shown in  FIGS. 7 and 8  the welding  82  is applied in the area of the tab  34  and slots  35  on the end of each segment that form the core plates. 
   Referring now to  FIG. 3B  a schematic illustration of a sheet  37  with guide holes  39  is shown. The sheet  37  is stamped with the first and second identical segments  33 A and  33 A′ and with different segment  33 B. The sheet has guide holes  39  for guiding the sheet  27  through a suitable stamping device (not shown). In such stamping operation, the stamping and/or punch out for segmenting and laminating steel core plates can be done in any suitable manner. The segments are then advanced to a knockout station. 
   As previously discussed, cam activated assemblies can be used to form the different shaped segment to allow for the odd, or B segment. For example, a first punch (not shown) is cycled for 2 press strokes to first punch out the A segment and then the A′ segment. Thereafter, a second punch (not shown) is activated for one stroke to punch the B segment. When the first cam punch segment is engaged, the cam second B punch segment is released and does not punch. According to one method of the present invention, a pad blanking processing can be used where the segment is pushed back into the strip. A knockout station, not shown, is used to punch out both the A, A′ and B segments. 
   In operation, the sheet of material  37  travels in the feed direction of the arrow such that a plurality of guide holes  39 , the plurality of tab-lock perforations  36  and projections  38  are first punched or stamped into the sheet  37 . The sheet  37  is then blanked using a cam activated punch, for example, to form the segments  33 A,  33 A′, and  33 B. Thereafter, the material is knocked out (not shown). 
     FIG. 4  is a schematic illustration showing one device and process for the assembly of the blank segments into a core plate. The material advances by the roller feed  60  to a servo indexing station  62  and then to the segmented blanking assembly  64  which comprises an indexing table. The assembled segments are then transferred to a stacking assembly  66 . It should be understood that various types of assembly apparatus can be used with the present invention. 
     FIGS. 5A ,  5 B,  5 C,  5 D,  5 E and  5 F are showing schematic illustrations of different joint designs for the tabs  34  and slots  35  which can be used with the blank segments of the present invention. It is important that the tabs  34  and slots  35  form an interlocking joint to secure the segments together so that the joint can effectively resist rotational forces generated during use of the stack  30  of core plates. Also, it should be understood that different punch and die orientations can be used with the present invention. 
     FIG. 6A  is a plan view showing a laminated and riveted core plate.  FIG. 6B  is a side elevation view and  FIG. 6C  is a cross-sectional view of an end of the laminated portion showing the projections  38  extending through a perforation and a lower core plate A. 
   The present invention also contemplates a stack of segment having partial segments missing in a stack of three or more which forms channels to allow flow through the clutch pack.  FIGS. 7 and 8  show a friction disc  80  having a stack of core plates formed of multiple segments. There is a first core plate  81  and a second core plate  83  with the first and second core plates having multiple segments as previously described. An interior core plate  87  is positioned between the first and second core plates. The interior core plate is also formed of multiple segments as previously discussed. However, at least one segment is missing on the interior core plate  87  and the at least one missing segment forms at least one channel  89  through the friction disk. The channel  89  allows lubrication fluid used with the friction disk to flow through the friction disk and more readily remove heat from the friction disk  80 . 
   The third embodiment provides openings that are stamped into the segments. The segments are stacked or laminated to intersect circumferentially and create offset radial channels or openings into opposite edges of the segment to form oil passages into the plate or disc.  FIGS. 9 and 10  shows a friction disk  90  having a stack of core plates formed of multiple segments as previously described. The friction disk  90  has two outer core plates  91  and a first interior core plate  93  and a second interior core plate  95  positioned in the stack between the two outer core plates  91 . At least one opening  96  is formed in the first interior core plate  93  and at least one opening  97  is formed in the second interior core plate  95 . The opening  96  on the first interior core plate  93  is disposed to be in alignment with the opening  97  in the second interior core plate  95  and the two openings form a passageway  99 . The passageway  99  allows lubricating fluid used with the friction disk to flow through the friction disk and remove heat from the friction disk  90 . It should be understood that the openings  96  and  97  can be formed to extend all the way through a portion of the core plate and would form a complete passageway through the friction disk. With such openings it would not be necessary to place the openings in alignment to form a passageway. With such openings it would also be possible to only use one interior core plate in the stack that forms the friction disk  90 . 
     FIGS. 11   a, b,  and  c.  show a single layer core plate utilizing the features of the invention. The core plate  111  has a plurality of teeth  112  and the teeth may be on either the inner or outer periphery of the core plate  111 . As shown in  FIG. 11   a,  the teeth are on the inner periphery of the core plate. The core plate  111  is comprised of three identical arucate segments  113 . Each segment  113  has a tab  114  and a slot  115  at opposing ends of the segment. The tab  114  and the slot  115  at either end are complimentary to and conformably receive a tab  114  or a slot  115  in the next adjacent segment. It should be understood that other shapes for the tab and slot arrangement can be useful for the segments shown in  FIGS. 11   a, b,  and  c . Such other shapes for the tab and slot arrangements are shown in  FIGS. 7   a  through  7   f  herein. As discussed previously in this patent application the segments  113  that form the core plate  111  can be identical in size or in certain applications the segments  113  can have slight variations so that they are not all identical in size. The parameters for the core plate  111  that determine whether the segments  113  are identical or will have slight variations in size have been previously discussed in this patent application. In addition, the segments  113  are formed in the same manner as previously described in this patent application. 
   Each segment  113  of the core plate  111  has a tab  114  and a slot  115  located on each end of the segment as previously described. The core plate  111  has a first surface  124  and a second surface  125  that in opposed spaced apart relationship with the first surface. The first and second surfaces of the core plate  111  are disposed to receive a friction material  128 . The friction material  128  can be positioned on either the first surface  124 , the second surface  125  or on both surfaces of the core plate  111 . The friction material  128  is positioned on the core plate  111  in a manner whereby the friction material overlaps the first and second ends of the arcuate segments that form the core plate. This positioning of the friction material provides additional resistance to separation of the core plate segments. The friction material  128 , as shown  FIG. 11   b , can be formed in a plurality of arcuate segments  129  where the arcuate segments have a first end  130  and a second end  131 . The segments  129  of the friction material  128  are positioned on the core plate  111  in a manner whereby the segments  129  overlap the tabs  114  and slots  115  that forms the joint between the adjacent segments  113  that form the core plate  111 . The friction material  128  can also be applied as a continuous annular ring on the first surface  124 , the second surface  125  or both the first and second surfaces of the core plate  111 . In this application the continuous annular ring of friction material  128  will cover the joints between the segments  113  of the core plate  111 . 
   If the friction material  128  is applied to the core plate  111  and segments  129 , the segments can be spaced apart to form grooves  133  for oil flow. It is also possible to form slots  134  in the core plate  111  where the slots are in alignment with the grooves  133  between the segments  129  of the friction material  128 . The grooves  133  and slots  134  act to provide a passage way to improve oil flow along the surface of the friction element formed by the core plate  111  and the friction material  128 . It is also possible to have apertures  136  that extend through the core plate  111  and the friction material  128 . The apertures extend from the first surface  124  to the second surface  125  of the core plate  111  continue through the friction material  128 . The apertures  136  allow oil to pass through the core plate  111  and the friction material  128  to equalize pressure that is present on either side of the friction element formed by the core plate  111  and the friction material  128 . 
   In forming a core plate  111  out of one group of segments  113  it is important that the joints formed between adjacent segments be strong enough to provide structural integrity for the core plate  111 . The friction material  128  that overlies the joints between the segments  113  on at least the first surface  124  or the second surface  125  of the core plate  111  provide some resistance to separation between the segments that form the core plate. However, the friction material  128  is used for its friction characteristics and not as a structural element that provides strength to the core plate  111 . To assist in providing structural integrity for the core plate  111  it has been found desirable to form the joint between adjacent segments  113  where the tab  114  and slot  115  interact to secure adjacent segments together. The configuration of the tab  114  and slot  115 , as shown in the drawings, provides an interlock between adjacent segments  113  that can resist separation of the adjacent segments. It has been found preferable to have the tab  114  and slot  115  configured in a way that there is a very tight interference fit between the tab and the slot to add resistance to separation between adjacent segments  113  of the core plate  111 . It is also possible to utilize welding, gluing, brazing and riveting in the area adjacent segments are joined together to further enhance the strength of the inner connection between adjacent segments  113  of the core plate  111 .  FIG. 12  shows a core plate  111  with welding, gluing or brazing  140  present on the joint between adjacent segments  113  of the core plate  111 .  FIG. 13  shows rivets  141  that have been utilized at the joint between adjacent segments  113  to add strength to the joint between adjacent segments that form the core plate  111 . 
   The above detailed description of the present invention is given for explanatory purposes. It will be apparent to those skilled in the art that numerous changes and modifications can be made without departing from the scope of the invention. Accordingly, the whole of the foregoing description is to be construed in an illustrative and not a limitative sense, the scope of the invention being defined solely by the appended claims.