Abstract:
One exemplary aspect of the present disclosure relates to a method of forming a friction material. The method includes depositing a plurality of particles on a substrate such that the particles provide a plurality of projections and channels between adjacent projections. This disclosure also relates to the friction material itself, and a system including a mechanical component and the friction material.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of prior U.S. patent application Ser. No. 14/638,508, filed Mar. 4, 2015, the entirety of which is herein incorporated by reference. The &#39;508 Application claims the benefit of U.S. Provisional Application No. 61/985,646, filed Apr. 29, 2014, the entirety of which is herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    Friction materials used in high torque applications need to withstand high temperatures. One example application is in the context of synchronizer rings, which are commonly found in manual and dual clutch transmissions. Synchronizer rings are known to include an outer surface having a plurality of gear teeth, and an inner surface having a friction material bonded thereto by way of an adhesive. 
         [0003]    One known type of friction material includes machined (i.e., cut) grooves. These friction materials include a consistent density and surface finish throughout. A second type of known friction material also includes pressed or molded grooves and a consistent surface finish throughout. However, unlike the first type, the material within the pressed/molded grooves has an increased density relative to the adjacent, raised material. 
       BRIEF DESCRIPTION OF THE DRAWINGS 
       [0004]    A method of forming a friction material according to an exemplary aspect of the present disclosure includes, among other things, depositing a plurality of particles on a substrate such that the particles provide a plurality of projections and channels between adjacent projections. 
         [0005]    A friction material according to an exemplary aspect of the present disclosure includes, among other things, a working layer provided by a plurality of particles. The working layer includes a first section having a first surface finish and a first density. The working layer further includes a second section having a second surface finish different than the first surface finish and a second density different than the first density. 
         [0006]    A system according to an exemplary aspect of the present disclosure includes, among other things, a mechanical component, and a friction material connected to the mechanical component. The friction material includes a working layer provided by a plurality of particles. The working layer further includes a first section having a first surface finish and a first density, and a second section having a second surface finish different than the first surface finish and a second density different than the first density. 
         [0007]    The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The drawings can be briefly described as follows: 
           [0009]      FIG. 1  illustrates an example mechanical component, which in this example is a synchronizer ring. 
           [0010]      FIG. 2  is a flow chart illustrating an example method of making the disclosed friction material. 
           [0011]      FIG. 3  schematically illustrates a hopper assembly, which may be used in the method of  FIG. 2 . 
           [0012]      FIGS. 4A-4B  are cross-sectional views of the example friction material, and illustrate the friction material at various stages of formation. 
           [0013]      FIG. 5  is a close-up view of the encircled area in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  illustrates an example mechanical component, which in the illustrated example is a synchronizer ring  10 . While a synchronizer ring  10  is illustrated, it should be understood that this disclosure extends beyond synchronizer rings. This disclosure is useful in other applications, such as other high torque applications, including, but not limited to, clutch plates and torque converters. 
         [0015]    The synchronizer ring  10  includes a plurality of gear teeth  12  extending from a radially outer surface  14  thereof. During operation, a radially inner surface  16  of the synchronizer ring  10  is exposed to large amounts of heat. The radially inner surface  16  includes a friction material  18  bonded thereto by way of an adhesive. The synchronizer ring  10  may be made of steel or brass, as examples. 
         [0016]      FIG. 2  illustrates an example method  20  for forming a friction material  18  according to this disclosure. In the method  20 , at step  22 , a plurality of particles  24  ( FIG. 3 ) are deposited onto a substrate  26 . The particles  24  may be selected from any number of materials including carbon, silica, glass, and vermiculite. The substrate  26  may be a carbon fiber weave, paper, textile, aramid, or cloth material, to name a few examples. In one example, the particles  24  are deposited onto the substrate  26  via a hopper  28  and a spreader  30 , which includes a plurality of elongate openings  32 , as illustrated in  FIG. 3 . A spreader  30  is not required in all examples. 
         [0017]    The result of step  22  is illustrated in  FIG. 4A . In  FIG. 4A , the friction material  18  includes the substrate  26  and a working layer  34 , which is provided by the particles  24 . The working layer  34  includes a plurality of projections  36  opposite the substrate  26 . The projections  36  are provided by the accumulation of particles caused by the elongate openings  32  in the spreader  30 . 
         [0018]    After step  22 , the projections  36  are naturally provided with a rounded contour  38 . Further, the projections  36  are spaced-apart by a distance D 1 . The distance D 1  can vary depending on the particular application (e.g., depending on the size of the synchronizer ring  10 ). In one example, the distance Di is within a range of 0.1875 to 0.5 inches. In one specific example, D 1  is 0.375 inches. 
         [0019]    The spaces between adjacent projections  36  define channels  40 . At the channels  40 , the friction material  18  has a height D 2 . The height D 2  may be relatively small in some examples. In particular, in one example, the distance D 2  may be such that the boundary of the channels  40  is provided by the substrate  26 . On the other hand, the friction material  18  has a height D 3  at the rounded contour  38  of the projections  36 . The distance D 3  is greater than the distance D 2 . 
         [0020]    After step  22 , a resin R (schematically shown in  FIG. 4A ) is applied to the friction material  18 , at step  42 . The particles  24  making up the working layer  34  absorb the resin R. Step  42  may be repeated to ensure an appropriate level of saturation. 
         [0021]    At step  44 , the projections  36  are machined (e.g., sanded) to essentially flatten the previously rounded contours  38 . The flattened height is shown at D 4 . The height D 4  is less than D 3  and greater than D 2  in one example.  FIG. 4A  shows, in phantom, the flat contour  46  of the projections  36 .  FIG. 4B  shows the machined projections  36  exhibiting the flat contour  46 . 
         [0022]    At step  48 , the friction material  18  is applied to the mechanical component, which in this example is the synchronizer ring  10 . In one example, which is schematically illustrated in  FIG. 5 , the friction material  18  is bonded to the radially inner surface  16  of the synchronizer ring  10  by an adhesive layer  50 . Heat H and pressure P are applied to the friction material  18 , the adhesive layer  50 , and the synchronizer ring  10  to ensure a proper bond. The adhesive layer  50  may be any known type of adhesive suitable for high temperature applications. The adhesive layer  50  is provided between an outer surface  51  of the friction material  18 , which is opposite a radially inner working surface  53  of the friction material  18 . 
         [0023]    The result of step  48  is shown in  FIG. 5 . In  FIG. 5 , the working layer  34  is compressed such that the friction material  18  has a substantially uniform height D 5  throughout. The height D 5  in one example is less than or equal to the height D 2 . 
         [0024]    When compressed, the working layer  34  has alternating first sections  52  and second sections  54 . In this example, the first sections  52  correspond to locations where the projections  36  were provided (projections  36  are illustrated in phantom in  FIG. 5 ). The second sections  54 , on the other hand, correspond to locations where the channels  40  were provided (channels  40  are shown in phantom in  FIG. 5 ). 
         [0025]    Because of the machining from step  44 , the first sections  52  have a first surface finish which is smoother than the surface finish of the second sections  54 . Since the second sections  54  are not machined in step  44 , the second sections  54  are left with a rougher, more granular surface finish (e.g., because of the unmachined nature of the deposited particles  24 ). 
         [0026]    Further, because the first sections  52  correspond to the locations where the projections  36  once existed, the first sections  52  are more dense than the second sections  54 . The reasons for this increase in density is twofold. First, there were more particles forming the projections  36  than in locations adjacent the channels  40 . Thus, at step  42 , more resin R was absorbed by the projections  36 . Second, even after step  44 , the flattened projections  36  had a height D 4  greater than the height D 2  adjacent the channels  40 . Thus, when compressed in step  48 , the particles within the first sections  52  are packed closer together than the particles in the second sections  54 . 
         [0027]    By providing the different first and second sections  52 ,  54 , the friction material  18  exhibits good wear characteristics because of the relatively smooth surface of the first sections  52  at the working surface  53 . The friction material  18  also exhibits good friction properties because of the granular surface finish of the second sections  54  at the working surface  53 . The friction properties of the second sections  54  are particularly beneficial for cold shifting, as the granular nature of the second sections  54  helps to break the cooling fluid (e.g., oil) film adjacent the radially inner surface  16  of the synchronizer ring  10 . 
         [0028]    Additionally, because the first section  52  has a higher density than the second sections  54 , cooling fluid is directed to the second sections  54 , and is allowed to permeate through the friction material  18  via the relatively lower density second sections  54 , which increases the cooling of the synchronizer ring  10  and the friction material  18  itself. This increase in cooling in turn increases performance of the synchronizer ring, and extends the life of both the synchronizer ring and the friction material. 
         [0029]    In the example of  FIG. 3 , the openings  32  are linear openings, which extend parallel to one another. This provides the friction material  18  with a plurality of linear, parallel first and second sections  52 ,  54 . Other patterns, such as zig-zags, come within the scope of this disclosure, however. While parallel first and second sections  52 ,  54  are mentioned above, the first and second sections  52 ,  54  may not be parallel when applied to the radially inner surface  16  of the synchronizer ring  10 , as the radially inner surface  16  may be conical. 
         [0030]    Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
         [0031]    One of ordinary skill in this art would understand that the above-described embodiments are exemplary and non-limiting. That is, modifications of this disclosure would come within the scope of the claims. Accordingly, the following claims should be studied to determine their true scope and content.