Abstract:
A method for forming a friction facing comprises placing a bonding powder mix in to a die, and placing a performance powder mix in to the die. Pressing the performance powder mix and the bonding powder mix creates a compact. Sintering the compact forms a friction facing. A clutch disc assembly can be formed. A clutch disc can comprise a mounting hole for securing a friction facing and a backer plate can comprise a pass-through hole. A mounting mechanism joins the mounting hole to the pass-through hole. The mounting mechanism comprises a head-height for a portion of the mounting mechanism that is mounted near the sintered compact. The bonding layer comprises a thickness corresponding to the head-height of the mounting mechanism.

Description:
FIELD 
       [0001]    This application relates to clutch disc friction facings and methods for forming the facing. 
       BACKGROUND 
       [0002]    Clutches can use discs having a friction facing. By pressing the friction facing against another surface, the disc provides a gripping function. The friction facings can be made of a material that wears over time due to the gripping and friction applied to the disc. The material can be expensive. 
       SUMMARY 
       [0003]    The methods and devices disclosed herein overcome the above disadvantages and improves the art by way of a method for forming a friction facing, comprising placing a bonding powder mix in to a die, and placing a performance powder mix in to the die. Pressing the performance powder mix and the bonding powder mix creates a compact. Sintering the compact forms a friction facing. 
         [0004]    A friction facing for a clutch disc comprises a bonding layer which omits copper, bronze, zirconium, and other friction modifiers and a performance layer which comprises copper, bronze, zirconium, and other friction modifiers. 
         [0005]    A friction facing for a clutch disc comprises a bonding layer which can have more or less of the binding materials than the performance layer. 
         [0006]    A clutch disc assembly comprises a mounting mechanism to secure a backing plate sintered together to the bonding layer of a dual layer friction facing to the core disc. The height of the bonding layer is comparable to the height of the coupling material used to secure the backing plate to the disc. The bonding layer height ranges from one-third to one-half of the total width of the dual friction facing. 
         [0007]    Additional objects and advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure. The objects and advantages will also be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
         [0008]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the claimed invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIGS. 1A and 1B  are views of a prior art disc. 
           [0010]      FIG. 1C  is a view of a prior art disc processing method. 
           [0011]      FIGS. 2A and 2B  are views of a dual layer facing disc. 
           [0012]      FIGS. 2C and 2D  are views of dual layer facing forming techniques. 
           [0013]      FIGS. 3A-3C  are views of a full-faced cushioned friction disc. 
           [0014]      FIG. 4  is an exploded view of a clutch disc assembly. 
           [0015]      FIG. 5  is a step flow diagram of a dual layer facing forming method. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Reference will now be made in detail to the examples which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Directional references such as “left” and “right” are for ease of reference to the figures and are not intended to limit the orientation of the disclosed devices and methods during use. 
         [0017]    In the prior art of  FIGS. 1A and 1B , a friction facing  15  on a disc assembly  10  is shown as a uniform layer. The facing has a total height H 2  from the backer plate  13  that is coupled to the disc  10  through a rivet  12 . An unusable thickness occurs because the rivet  12  protrudes on the backer plate  13  to height H 1 . 
         [0018]    In  FIGS. 2A and 2B , a dual layer friction facing  215  on a disc assembly  200  is shown. The facing  215  has a first layer  206  attached to a front surface of a backer plate  130 . The first layer  206  has a height of H 1 . The first layer  206  and second layer  211  have a combined height of H 2 . H 2  is the total height of the friction facing  215 . The second layer  211  has a height of H 2  minus H 1  equal to H 3 . The usable life of the friction facing is complete when substantially all of the second layer  211  has worn off due to losses during gripping. The backer plate  130  is mounted to the core plate of the disc assembly  200  by use of a rivet  120 . The rivet  120  is an example of a mounting mechanism. Other mounting mechanisms are solder, bolts and screws, or the like. The rivet  120  has a head-height that protrudes from the core plate of the disc assembly  200  and the backer plate  130 . H 1 , the height of the first layer  206 , is comparable to the resulting head-height from the protruding rivet  120 . 
         [0019]    In the prior art process of  FIG. 1C , a friction facing is assembled in a die  16 . The compact  17  of friction facing material is formed by putting a powder mixture  14  in to the die  16  and pressing the powder mixture using a pressing mechanism  15 . Sintering the compact  17  adheres the powder together to form the friction facing  15 . This technique forms a single layer friction facing  15  with homogenous mix throughout the entire thickness. 
         [0020]    In  FIG. 2C  a dual layer ceramic technique is shown to form a dual layer compact  171  with a bonding layer  205  and performance layer  210 . The die  160  receives a first layer of a bonding mix  235  that is processed through a raw material holding container  230  and then a mixer  231 . The bonding mix  235  can omit or reduce expensive materials such as copper, bronze, zirconium, and certain other friction modifiers since it does not need to provide grip. So, materials that augment grip can be omitted. Instead, the bonding mix  235  can include materials that augment the adhesion of the friction facing to the disc  200 . The disc  200  can comprise a backing plate  130 , and the bonding layer  205  can be attached to the backing plate  130 . 
         [0021]    A performance mix  240  is applied over the bonding mix  235  to form the required height H 2  for the friction facing  215 . The performance mix  240  can also have a holding container  241  and mixer  242 . The dual layers formed by the bonding layer  205  and performance layer  210  can create the requisite “button” or “compact”  171  for forming a friction facing  215  for a friction disc. The performance mix  240  can comprise expensive materials such as copper, bronze, zirconium, and certain other friction modifiers in a greater quantity than the bonding layer. This maintains the superior performance of the friction facing  215  while reducing costs. 
         [0022]    The dual layer ceramic technique places the powder mix  235  for the bonding layer  205  in to the die  160  and then places the powder mix  240  for performance layer  210  in to the die  160 . A leveling step can smooth the bonding layer prior to applying the performance layer, and a second levelling step can smooth the performance layer prior to pressing. Levelling can compromise scraping with a blade, or other mechanical devices and techniques. A press  150  is used to create a dual layer compact  171 . A weight measurement device  250  can be used to ensure that the correct amount of material has been included in the compact. Weight measurement can occur after pressing to form the compact or during of intermittently during the addition of the powder mixes  235 ,  240  and brazing or other material addition from sprayer  209 . Weight measurement can be done during or after the addition of each the powder mixes, brazing material or other material applications to check whether additional material is needed, or to check whether there is too much material. 
         [0023]    If the compact meets specifications for weight, a backer plate is introduced. As one example, a steel backer plate  255  is shown, though other backer plated can be used. For example, a copper-plated backer plate can be used. The backer plate  255  and compact are put together utilizing devices for backer plate and facing affiliation  260 . Sintering in sintering furnace  270  adheres the materials in to a friction facing  215  with a final bonding layer  206  and final performance layer  211 . Post-processing steps and devices can include a coining device and measurement device  280 . The coining and measurement device can comprise separate or integrated devices. When the friction facing meets post-sintering specifications, it is sent to packaging equipment  290  for packaging. Packaging can comprise assembly in to a clutch device or aftermarket friction facing packaging. 
         [0024]    By maintaining the ratio of the thickness of the two layers of materials prior to compact press, it is possible to ensure that the bonding layer mix  235  does not come out during the sintering process. The ratio of bonding layer to performance layer can be maintained, in part, by having two separate powder mix inputs from mixers  231  and  242  respectively. 
         [0025]    The above dual layer ceramic technique and resulting device can be used in many applications, including in dry clutches. 
         [0026]      FIG. 5  outlines a method for forming a dual layer sintered facing through a step flow diagram comprising of steps S 101 -S 115 . At process start-up, a die can be chosen to receive a powder mix of the desired materials for a bonding layer in step S 101 . A leveling step S 103  is performed to smooth the bonding layer prior to applying the performance layer in step  107 , and a second levelling step  109  can smooth the performance layer prior to pressing in step S 111 . Levelling can compromise scraping with a blade, or other mechanical devices and techniques. The two layers are then pressed to form a final compact on step S 111 . This compact can be applied to a desired backer plate in step S 112  and then processed to be sintered together in step  113 . In step S 115 , a variety of post-processing activities such as coining, pressing, grinding, shot blasting, and measurements can be performed. 
         [0027]    A variant of the dual layer sintered facing method in the step flow diagram of  FIG. 5  is shown by adding a pressing step S 104  after leveling the bonding layer in step S 103 . Then, a brazing layer is applied over the bonding layer in step S 106  prior to placing the performance powder mix in step  107  in to the die. 
         [0028]    Turning to  FIG. 2D , the dual layer friction facing technique can include a brazing layer application. A brazing mechanism, such as sprayer  209 , can be used to apply a brazing material to the bonding layer. The brazing material can be a power, or, as illustrated, a sprayed liquid. The brazing material can be applied to the pressed single layer compact  170 , which is illustrated as the bonding layer, prior to adding a performance powder mix  240  in the die  160 . A dual layer compact  171  is formed by pressing the performance powder mix to form the performance layer. 
         [0029]    Depending on the required attributes of the final friction facing material, and depending on the desired order of layer application, a die  160  can be chosen to form the single layer compact  170  and then the dual layer compact  171 . In one aspect, the performance powder mix can be added to the die first. Pressing or leveling can occur to form performance layer. Then, the bonding powder mix can be applied, with or without intervening brazing layer application from sprayer  209 . Or, as drawn, the bonding layer can be formed in the die prior to applying the performance layer. Thus, the dual layer compact  171  can be formed from either the bonding mix  235  or performance mix  240  being placed one on top of the other and pressed before being sintered. 
         [0030]    The disclosed techniques to form a dual layer friction facing can be streamlined to meet the final requirements of a dry clutch assembly. For this purpose, it is possible to place the final dual layer compact  171  as shown in  FIG. 2D  over a backer plate  130  and sintering the backer plate  130  together with the dual layer facing. 
         [0031]    The value of the dual layer friction facing technique is in the resulting facing material  215  that has both the bonding layer  206  with materials to augment adhesive properties to attach to another surface and using less of the expensive friction modifiers, while also maintaining the high performance gripping function through its performance layer  211 . The bonding mix  235  can have iron, fillers, and materials to achieve proper binding with both the performance layer  211  on one end and the backer plate  130  or core plate  200  on the other. The performance mix  240  can have higher copper, bronze, zirconium or other related materials to meet the performance requirements such as coefficient of friction and wear necessary for the friction facing surface. Both powder mixes can have materials required for proper binding strength and dimensional stability between the two layers. Some non limiting examples of the types of materials and percentage of material ranges for the bonding and performance mix are shown in the table below. Other percentages can be used based on the intended application of the friction facing. 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                   
                 Bonding 
                 Performance 
               
               
                 Material 
                 Layer 
                 layer 
               
               
                   
               
             
             
               
                 Copper 
                 15-20%  
                 65-70% 
               
               
                 Iron 
                 45-50%  
                  4-5% 
               
               
                 Tin 
                 3-5% 
                  1-3% 
               
               
                 Graphite 
                 5-7% 
                  5-7.5% 
               
               
                 Zironium 
                 9-11%  
                 10-12% 
               
               
                 Quartz (SiO2) 
                 1-2% 
                 0.1-.25%     
               
               
                 Silicon Carbide 
                     5% 
                 — 
               
               
                 Others 
                 — 
                     2% 
               
               
                 (Al O2, Kyanite, Mullite, Cristobalite) 
               
               
                   
               
             
          
         
       
     
         [0032]    A friction facing for a clutch disc can be formed from the dual layer sintered facing techniques disclosed. It is possible to have a friction facing material  215  with a bonding layer  206  with less of the expensive friction modifiers such as copper, bronze, and zirconium than the performance layer  211 . Similarly, by tailoring the composition of the powder mixes, the bonding layer  206  of the friction facing  215  can have either more or less of the binding materials as compared to the performance layer  211 . It is also possible to have a friction facing  215  formed by having a brazing layer between the bonding layer and the performance layer prior to both being pressed together as shown in  FIG. 2D . An additional layer of material can be applied over the performance layer  211 , and can be the same brazing material or a different performance material applied by a sprayer  209 . The material applied to the performance layer can be of a type that permeates the performance layer during the sintering process. A dual layer friction facing can also have a first bonding layer with height H 1  which can range from one-third to one-half of the total height H 2 , H 2  being the distance from one end of the bonding layer to the opposite end of the performance layer. 
         [0033]    A single disc clutch or a dual disc clutch can benefit from the friction materials disclosed herein. The friction discs can be puck-style as shown in  FIG. 2A  or full-facing style.  FIG. 3A  shows a full-facing cushioned friction disc assembly  300 . By modifying the die  160  used to form the compact, a full-facing friction material can be formed. Or, a pattern  325  of compacts can be assembled in to a full-facing friction disc assembly  300 . The cushioned friction disc assembly may comprise a ceramic material on a first side  215 , and an organic material on a second side  116  as shown in  FIGS. 3B and 3C . A cushion assembly  321  can be assembled between the first side and the second side. The cushion assembly can comprise mounting mechanisms such as  120  and  121 . The height H 1  of the bonding layer can be chosen based on the height of the mounting mechanisms, and the height and content of the performance layer can be chosen based on the intended usable life of the friction disc or based on the performance requirements. 
         [0034]    A cushion assembly disc can take advantage of a dual layer friction facing as disclosed herein in  FIG. 3C  to have a friction facing  215  with a first bonding layer  206  and a second performance layer  211 . A bonding layer  206  can have a height comparable to the head-height resulting from the protruding mounting mechanism  120 . 
         [0035]    A clutch disc assembly can be part of the clutch systems to transfer torque from an engine to a transmission or another driveline component.  FIG. 4  shows a 2-disc clutch assembly with a front disc  200 , an intermediate disk  450 , a rear disc  400 , and a cover assembly  480 . A left plane of the front disc can of be coupled to a flywheel of an engine to rotate. A right plane of the clutch cover  480  can be oriented towards the transmission, and can connect to mechanisms, such as a release bearing assembly or like device, to engage and disengage the clutch components. The clutch can be a push or pull type, and can comprise other actuators, such as a catapult linkage, a concentric actuator, an electric actuator, mechanical rod, hydraulic system, or the like. The clutch can be adjustable or wear through, and can comprise a variety of clutch friction discs. The discs can vary in spline size, facing type, number of facings, cushion rate, damper rate, damper assembly  330 , facing material and can optionally comprise pre-damper mechanisms, among other variables. A center axis A can be surrounded by an input shaft for coupling to the transmission. A hub and other customary clutch components can be arranged for torque transfer and to couple to the clutch friction discs and damper mechanisms. 
         [0036]    Turning to  FIG. 4 , the friction material can be assembled in to a clutch assembly having a puck-style. The number of pucks can vary from the four illustrated to a number of pucks. Typically, from 3 to 6 pucks are used, though other numbers may be used based on application, such as 8 or 12. 
         [0037]    Friction disc  200  can comprise a friction material  215  configured to engage with the flywheel when the clutch is engaged. A rear friction material  216  is configured to grip a first side  451  of the intermediate plate  450 . A second friction disc  400  is configured to grip a second side  452  of the intermediate plate  450 . A rear side  416  of the second friction disc  400  is configured to grip a pressure plate  485 . The pressure plate  485  is actuated by any one of a number of actuators. The pressure plate  485  can move to compress the first friction disc  200 , intermediate plate  450 , and second friction disc  400  together and towards the flywheel. When compressed, torque is transferred from the flywheel to a central hub, and from the central hub to the transmission or another driveline component. 
         [0038]    The clutch disc assembly example in  FIG. 4  shows puck-style front and rear discs with friction facing materials that are attached to backing plates  130  and connected to the disc surface  200  or  400  through a mounting mechanism  120 . It is noted that a dual layer friction material can be formed under the disclosed method herein by using a die  160  tailored to meet the geometry of the discs  200  and  400 . A dual layer compact  171  formed by pressing the bonding mix layer  205  and performance mix layer  210  can be placed such that the bonding layer meets the surface of the backer plate  130  prior to being sintered together. The height H 1  of the sintered bonding layer  206  atop the backer plate  130  can be chosen to correspond to the height of the protruding mounting mechanism  120 . This height H 1  can also be around one-third to one-half of the total height H 2  of the sintered dual layer friction material  215 . 
         [0039]    It is possible that a clutch disk with the dual layer friction facing material  215  has the performance layer  211  with friction modifiers from one or more of copper, bronze, and zirconium. Similarly, it is possible to use the dual layer sintered method disclosed to configure the materials in the bonding layer mix and the performance layer mix where one has more or less of the binding materials that the other. 
         [0040]    In the preceding specification, various aspects of the methods and devices disclosed herein have been described with reference to the accompanying drawings. Other implementations will be apparent to those skilled in the art from consideration of the specification and practice of the examples disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims.