Patent Abstract:
The present invention is directed to apply plates, clutch plates, reaction plates and backing plates utilized of friction clutch packs, brake housings, clutch hubs, clutch housings, accumulators, spline sets, valve bodies and wear surfaces against which bushings, seals, springs and similar components slide and contact which are utilized in motor vehicle automatic transmissions, are fabricated of aluminum and include an electro ceramic coating deposited thereon. Such components exhibit reduced weight relative to similar components fabricated of steel as well as extended service life due to both the hardness and porosity of the ceramic coating.

Full Description:
FIELD 
       [0001]    The present disclosure relates to electro ceramic coated aluminum components and more particularly to electro ceramic coated aluminum components such as clutch hubs, clutch and brake housings, plates and similar components utilized in motor vehicle powertrains, particularly transmissions. 
       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]    Many motor vehicle powertrain components have been and are fabricated of steel because of its strength, malleability, cost and availability. This is not to say, however, that all its engineering attributes are positive or desirable. One of its most commonly recognized drawbacks is its weight, especially when compared to materials such as aluminum and magnesium. 
         [0004]    A conventional motor vehicle automatic transmission may include one or more friction clutch assemblies, planetary gear assemblies, band brakes, accumulators, spline sets, valve bodies and wear surfaces engaged by bushings, seals, springs and similar components. A conventional friction clutch includes a friction clutch pack having alternating friction plates and reaction plates, both typically fabricated of steel, disposed between an apply plate and a backing plate against which the friction clutch pack is compressed. When compressed, torque is transferred through the friction clutch pack between an inner hub and an outer housing. Band brakes comprehend a circumferential band having friction material which partially encircles a rotating cylindrical body which may be a housing or similar component. One end of the brake band is fixed and the other end is coupled to an actuator which tightens the band about the cylindrical body. 
         [0005]    Between the clutch hub or housing and other components such as shafts, quills or planetary gear components, it is often necessary to establish a fluid tight seal in order to either separate fluid filled, i.e., wet, areas from dry areas or to establish a flow path for fluid across or between rotating and non-rotating components. This may be achieved by, in the first case, a resilient seal disposed in a channel or groove between the areas or, in the second case, utilizing a pair of resilient seals disposed in grooves on both sides of the flow path to properly direct fluid flow. Also, one or both of the inner hub and outer housing may be coupled to a shaft or quill by splines. 
         [0006]    Conventionally, friction clutch plates, band brake cylinders, hubs, housings, spline sets and components having surfaces engaged by friction material or resilient seals have been fabricated of various steels due to the strength and durability these materials. Not only does steel provide the structural integrity necessary to carry the torque loads encountered by such components but it also provides the durability of the faces or surfaces exposed to frictional (sliding) forces. As noted, the primary drawback of such steel clutch components is weight. However, since many of these transmission components both contribute to the total vehicle weight and rotate and thus contribute to powertrain energy loss as they are repeatedly accelerated and decelerated, they twice contribute to fuel consumption. Accordingly, any weight reduction of a rotating component, such as a clutch or other transmission component, positively affects fuel consumption, both from the standpoint of total vehicle weight as well as powertrain efficiency. 
         [0007]    One solution to the weight problem is the substitution of a lighter weight material such as aluminum or magnesium. Aluminum has about one-third the density of steel and exhibits good heat transfer, both characteristics being important in transmissions, especially clutches and brakes. However, it has been found that this material is unsuitable because the surfaces exposed to frictional forces during clutch and brake engagement as well as those exposed to sliding forces such as seals and valve surfaces exhibit unacceptable wear and thus unacceptable service life. 
       SUMMARY 
       [0008]    The present invention is directed to apply plates, clutch plates and reaction plates utilized of friction clutch packs, brake housings, clutch hubs, clutch housings, accumulators, spline sets, valve bodies and wear surfaces against which bushings, seals, springs and similar components slide and contact which are utilized in motor vehicle automatic transmissions and are fabricated of aluminum which include an electro ceramic coating deposited thereon. Such components exhibit reduced weight relative to similar components fabricated of steel as well as extended service life due to both the hardness and porosity of the ceramic coating. 
         [0009]    Thus it is an aspect of the present invention to provide an apply plate for a friction clutch pack having an electro ceramic coating on one surface. 
         [0010]    It is a further aspect of the present invention to provide a reaction plate for a friction clutch pack having an electro ceramic coating on both surfaces. 
         [0011]    It is a still further aspect of the present invention to provide a backing plate for a friction clutch pack having an electro ceramic coating on one surface. 
         [0012]    It is a still further aspect of the present invention to provide a band brake assembly having an electro ceramic coating on an outer surface of a cylindrical body. 
         [0013]    It is a still further aspect of the present invention to provide a accumulator having an aluminum housing and an electro ceramic coating on an inner surface. 
         [0014]    It is a still further aspect of the present invention to provide bushing interface surfaces on aluminum hubs and housings having an electro ceramic coating. 
         [0015]    It is a still further aspect of the present invention to provide spring wear surfaces on aluminum pistons and dams having an electro ceramic coating. 
         [0016]    It is a still further aspect of the present invention to provide seal grooves and seal surfaces adjacent fluid passageways in clutch feed hubs and housings having an electro ceramic coating. 
         [0017]    It is a still further aspect of the present invention to provide male and female spline surfaces on aluminum clutch housings and hubs having an electro ceramic coating. 
         [0018]    It is a still further aspect of the present invention to provide thrust surfaces on aluminum hub, housings and supports having an electro ceramic coating. 
         [0019]    It is a still further aspect of the present invention to provide an aluminum valve body with bore surfaces having an electro ceramic coating. 
         [0020]    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 
         [0021]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0022]      FIG. 1  is a fragmentary sectional view of a portion of an automatic transmission including a friction clutch pack having components including an electro ceramic coating; 
           [0023]      FIG. 2  is an enlarged sectional view of a portion of a friction clutch pack assembly including an apply plate, reaction plates and a backing plate including an electro ceramic coating; 
           [0024]      FIG. 3  is an enlarged fragmentary perspective view of an aluminum apply plate including electro ceramic coatings on both faces according to the present invention; 
           [0025]      FIG. 4  is an enlarged fragmentary perspective view of an aluminum reaction plate including electro ceramic coatings on both faces according to the present invention; 
           [0026]      FIG. 5  is an enlarged fragmentary perspective view of a powdered metal aluminum backing plate including a electro ceramic coating on one face according to the present invention; 
           [0027]      FIG. 6  is an enlarged fragmentary perspective view of single sided aluminum clutch plates and reaction plates including electro ceramic coatings on both faces and friction material on one face according to the present invention; 
           [0028]      FIG. 7  is a full sectional view of a fluid accumulator utilized in, for example, an automatic transmission having an inner surface coated with an electro ceramic coating according to the present invention; 
           [0029]      FIG. 8  is a full sectional view of a portion of an automatic transmission having a band brake assembly with an outer drum or housing surface coated with an electro ceramic coating according to the present invention; 
           [0030]      FIG. 9  is a schematic end view of the band brake drum assembly of  FIG. 8  with an outer drum or housing surface coated with an electro ceramic coating according to the present invention; 
           [0031]      FIG. 10  is a full sectional view of a portion of an automatic transmission including an aluminum clutch housing or support having an electro ceramic coating on its interior and exterior surfaces according to the present invention; 
           [0032]      FIG. 11  is a perspective view of a valve body of an automatic transmission including valve bores and valves having an electro ceramic coating on the interior surfaces of the valve bores and the exterior surfaces of the valves according to the present invention; 
           [0033]      FIG. 12  is a full sectional view of a portion of an automatic transmission including a friction clutch pack and hydraulic actuator having an electro ceramic coating on wear surfaces according to the present invention; 
           [0034]      FIG. 13  is a full sectional view of a portion of an automatic transmission including a friction clutch pack, hydraulic actuator and planetary gear assembly having an electro ceramic coating on wear surfaces according to the present invention; and 
           [0035]      FIG. 14  is a flow chart illustrating the steps undertaken to provide an electro ceramic coating on the aluminum components illustrated in  FIGS. 1 through 13 . 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0037]    With reference to  FIG. 1 , a portion of a motor vehicle automatic transmission is illustrated and generally designated by the reference number  10 . The automatic transmission  10  includes a housing  12  which mounts, supports, positions and protects various components such as shafts and quills  14 , a plurality of planetary gear assemblies  16 , one of which is illustrated in  FIG. 1 , fluid passageways  18  and a plurality of friction clutch assemblies  20 . 
         [0038]    Referring now to  FIGS. 1 and 2 , the friction clutch pack assemblies  20  include an apply plate  22  having male splines  24  disposed about its periphery which engage a plurality of female splines  58  within an outer housing  60  and thus rotate therewith. The apply plate  22  is acted upon and axially translated by a linkage or member  28  driven by a hydraulic operator or actuator  30 . The friction pack assemblies  20  also include a first plurality of friction plates or discs  32  having female splines  34  which engage complementary male splines  36  on an inner hub  40  and thus rotate therewith. The first plurality of friction plates or discs  32  are conventional and include friction facing material  42  on both faces or surfaces. The first plurality of friction plates or discs  32  are interleaved with a second plurality of reaction plates or discs  52 . The reaction plates or discs  52  include male splines  56  disposed about their peripheries which are complementary to and engage the plurality of female splines  58  within the outer housing  60  and thus rotate therewith. At the opposite end from the apply plate  22  is a backing plate  62  against which the friction plates  32  and reaction plates  52  are compressed by the hydraulic operator  30 . When so compressed, torque may be transmitted between the inner hub  40  and the outer housing  60 . 
         [0039]    Referring now to  FIG. 3 , the apply plate  22  is stamped or extruded of aluminum or an aluminum alloy, or may be powdered metal (PM) aluminum and, as stated above, includes male splines  24  about its periphery. The front and rear faces or surfaces of the apply plate  22  include an electro ceramic coating  28 . The electro ceramic coating  28  is preferably a material such as titanium dioxide and is applied by the process described below. The approximate thickness of the ceramic coating  28  may from 0.005 to 0.050 mm. (0.000197 to 0.00197 inches), but it may be thicker or thinner as needed for performance. 
         [0040]    Referring now to  FIG. 4 , the reaction plate or disc  52  is also stamped or extruded aluminum or an aluminum alloy and, as stated above, includes male splines  56  about its periphery. Typically, the reaction plate or disc  52  is between about 1.5 mm. to 3.0 mm. (0.059 to 0.118 inches) in thickness. The front and rear faces or surfaces of the reaction plate or disc  52  also include an electro ceramic coating  54 . The electro ceramic coating  54  may be applied to the aluminum or aluminum sheet stock before stamping, if desired. The electro ceramic coating  54  is preferably titanium dioxide and is applied by and through the process described below. The approximate finished thickness of the ceramic coating is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but may be thicker or thinner. 
         [0041]    Referring now to  FIG. 5 , the backing plate  62  also includes male splines  64  which are complementary to and engage the female splines  58  within the outer housing  60  and thus it rotates with the outer housing  60 . The backing plate  62  is preferably fabricated of powdered metal (PM) aluminum, stamped and machined aluminum, forged and machined aluminum or extruded aluminum. The front face or surface  66  of the backing plate  62  also includes an electro ceramic coating  68 . The approximate finished thickness of the ceramic coating is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but may be thicker or thinner. 
         [0042]    It should be appreciated the with regard to the apply plates  22 , the reaction plates  52  and the backing plates  62 , no secondary surface finishing is needed for thin to medium thickness electro ceramic coatings  28 ,  54  and  68  but secondary surface finishing after coating may be desirable to tailor the micro surface finish to provide a smoother or rougher micro surface finish to improve clutch friction carrying ability and clutch feel. 
         [0043]    Because the apply plates  22 , the reaction plates  52  and the backing plates  62  having surfaces with an electro ceramic coating according to the present invention replace or retrofit, both functionally and dimensionally, previously utilized components, they may be readily installed in place of such components. Thus, without requiring other engineering or design changes, the benefits they confer, primarily weight and energy savings, are immediately available. For example, in one automatic transmission, substitution of the apply plates  22 , the reaction plates  52  and the backing plates  62  in the several clutches results in a weight saving of 1.8 Kg. (3.97 pounds). 
         [0044]    With reference now to  FIGS. 2 and 6 , as an alternative to friction clutches having a plurality of friction plates  32  including friction material  42  on both faces alternating with reaction plates  52 , certain friction clutches utilize single sided friction plates  80  having male splines  82  and an electro ceramic coating  84  on both faces or surfaces and friction facing material  86  on only one face or surface. The single sided aluminum or aluminum alloy friction plates  82  are interleaved with a like plurality of aluminum or aluminum alloy reaction plates  90  having female splines  92  and an electro ceramic coating  84  on both faces or surfaces and friction material  86  on only one face or surface. The electro ceramic coating  84 , which is also preferably applied to the splines  82  and  92 , on these single sided plates  80  and  90  provides an excellent surface upon which an adhesive and the friction material  86  is applied. 
         [0045]    It will be appreciated that in addition to disclosing single sided clutch plates,  FIG. 6  illustrates components for what is referred to as an inverted clutch design wherein the friction plates  80  include male splines  82  which mate with the splines  58  on the outer housing  60  and the reaction plates  90  include female spines  92  which mate with the male splines  36  on the inner hub  40 . It should be understood that either arrangement of the friction facing material  42  and  86 , i.e., single sided or double sided, may be utilized with either the conventional friction clutch configuration of  FIGS. 1 and 2  or the inverted configuration of  FIG. 6 . 
         [0046]    Referring now to  FIG. 7 , a fluid accumulator  100  which may be a component of the automatic transmission  10  of  FIG. 1  includes a cylindrical housing  102  having a substantially closed end having an inlet/outlet port  104  which communicates with a fluid chamber  106 , an open end which is closed and sealed by a threaded end plug  108  and cylindrical interior wall or surface  110 . The housing  102  may include various mounting or attachment members such as the arms  112 . Disposed within the cylindrical housing  102  is a piston  114  having one or more circumferential grooves  116  which receive elastomeric seals  118  which contact and seal against the cylindrical interior wall or surface  110 . Between the piston  114  and the end plug  108  are a pair of concentrically disposed compression springs  120 . In conventional fashion, the compression springs  120  provide a biasing force to the piston  114  in the direction of the inlet/outlet port  104 . When fluid pressure in the chamber  106  overcomes the force of the springs  120 , the piston moves to the right in  FIG. 7 , enlarging the volume of the fluid chamber  106  and vice versa. The cylindrical interior wall or surface  110  includes an electro ceramic coating  124  having a thickness of between 005 to 0.050 mm. (0.000197 to 0.00197 inches) or more or less depending upon engineering considerations which is applied as described below. 
         [0047]    Referring now to  FIGS. 8 and 9 , a portion of another motor vehicle automatic transmission is illustrated and generally designated by the reference number  150 . The automatic transmission  150  includes a housing  152  which mounts, positions and protects various components such as an input shaft  154 , a concentric quill  156 , a plurality of planetary gear assemblies  158 , one of which is illustrated in  FIG. 8 , fluid passageways  162  and a plurality of friction clutch assemblies  164 , one of which is also illustrated in  FIG. 8 . 
         [0048]    The automatic transmission  150  also includes a band brake assembly  170  which generally surrounds the aforementioned components which rotate on the axis of the input shaft  154  and the quill  156 . The band brake assembly  170  includes a bell or cylindrical housing  172  which is supported on an anti-friction bearing  174  such as a ball or roller bearing assembly and is coupled for rotation with a component such as a planet gear carrier  176  of the planetary gear assembly  158 . The cylindrical housing  172  of the band brake assembly  170  may take different forms or shapes such as axially shorter or longer or with a uniform outside diameter and the configuration illustrated should be understood to be exemplary and not limiting. 
         [0049]    The cylindrical housing  172  includes a fully circumferentially extending outer annular friction surface  180  which is generally surrounded by a brake band  182 . The brake band  182  includes clutch or brake friction material  184  on its inner surface facing and adjacent the outer friction surface  180  of the cylindrical housing  172 . One end of the brake band  182  is secured to the transmission housing  152  by a suitable attachment device or fastener  185  and the other end includes a lug or ear  186  which is engaged by a shaft, rod or output member  188  of a bi-directional linear actuator  190 . The linear actuator  190 , which may be hydraulically, electrically or pneumatically operated, may be under the control of a transmission control module (TCM) or similar engine or vehicular controller (all not illustrated) which controls the action of the actuator  190  and tightens the brake band  182  about the friction surface  180  of the cylindrical housing  172  to terminate or inhibit rotation of the housing  172  and any coupled or connected component or components and relaxes the brake band  182  to allow rotation thereof. 
         [0050]    The cylindrical housing  172  is fabricated of aluminum such as 5052 or 6061 aluminum or a similar alloy and the outer annular friction surface  180  of the cylindrical housing  172  includes an electro ceramic coating  194  which is applied according to the process described below. The electro ceramic coating  194  on the housing  172  may be polished or finished, both as needed and depending upon the thickness of the ceramic coating  194 , in order to obtain a required surface finish. The approximate finished thickness of the ceramic coating  194  is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but it may be thicker or thinner. The cylindrical housing  172  of the band brake assembly  170  thus provides the weight saving and low inertia advantages of aluminum as well as improved durability and service life. 
         [0051]    Referring now to  FIG. 10 , another portion of a motor vehicle automatic transmission is illustrated and generally designated by the reference number  200 . The automatic transmission  200  includes a housing  212 , a rotating shaft or quill  214 , a plurality of planetary gear assemblies (not illustrated), a plurality of fluid passageways  216  and a plurality of friction clutch assemblies  218 , one of which is illustrated in  FIG. 10 . The friction clutch assembly  218  includes a balanced hydraulic operator or actuator  220  having hydraulic fluid chambers  224  contained within a unitary aluminum housing and hub assembly  230 . The hydraulic fluid chambers  224  are selectively provided with pressurized hydraulic fluid through the fluid passageways  216  to engage and release the friction clutch assembly  218  and transmit torque therethrough. Three resilient seals  226  in corresponding grooves  228  adjacent the fluid passageways  216  tightly seal and isolate the fluid passageways  216  and direct hydraulic fluid to the chambers  224  of the hydraulic operator or actuator  220   
         [0052]    A unitary aluminum housing and hub assembly  230  preferably combines into one component an “L” shaped housing portion  232  which extends radially and axially on the outside of the friction clutch assembly  218  and an irregular, generally cylindrical hub portion  234  which extends axially on the inside of the friction clutch assembly  218 . The housing portion  232  of the housing and hub assembly  230  includes a plurality of female splines  236  which engage and couple a plurality of reaction plates  238  in the friction clutch assembly  218  to the housing and hub assembly  230 . The hub portion  234  of the housing and hub assembly  230  also includes a plurality of female splines  240  which mate with a plurality of complementary male splines  244  on the shaft or quill  214  to transmit torque therebetween. The hub portion  234  further includes bushing and rotating seal surfaces  246  which rotationally and frictionally contact resilient seals  226  and adjacent bushings as well as a thrust surface or shoulder  248 . 
         [0053]    The pluralities of female splines  236  and  240  as well as the bushing and rotating seal surfaces  246  and the thrust surface or shoulder  248  include an electro ceramic coating  250  which is applied according to the process set forth below. Conveniently and practically, the entire inner and outer surfaces of the unitary aluminum housing and hub assembly  230  may be coated with the electro ceramic coating  250 . The electro ceramic coating  250  on the pluralities of female splines  236  and  240  provides a surface that has good surface hardness which withstands mating with a splined steel shaft or clutch plates which are typically steel but could be aluminum with an electro ceramic coating as described above. The approximate thickness of the ceramic coating  250  is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but it may be thicker or thinner. 
         [0054]    With regard to the electro ceramic coating  250  on the bushing and rotating seal surfaces  246  and the thrust surface or shoulder  248 , these surfaces may be polished or finished if needed depending the thickness of the electro ceramic coating  250  in order to obtain the required surface finish. Again, the approximate thickness of the ceramic coating  250  is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but it may be thicker or thinner. 
         [0055]    The electro ceramic coated unitary aluminum housing and hub assembly  230  combines into a single lightweight and durable aluminum component what was heretofore two components including a steel hub which was riveted to or serrated and press fit onto the housing. Additionally, the unitary aluminum housing and hub assembly  230  provides weight savings in a component that may be retrofit into the same applications and occupies the same or less packaging space. 
         [0056]    Referring now to  FIG. 11 , a typical and exemplary valve body of an automatic transmission is illustrated and generally designated by the reference number  300 . The valve body  300  which is secured to the bottom portion of an automatic transmission (not illustrated) is typically cast aluminum and includes myriad ports and passageways  302  which provide fluid communication between, for example, a housing  304  of a hydraulic pump and a plurality of valve bores  306  as well as numerous internal hydraulically controlled and actuated components of the transmission. The plurality of valve bores  306  receive a like plurality of valves or valve spools  310  which are also commonly fabricated of aluminum. The valves or valve spools  310  include an electro ceramic coating  312  over their entire exterior which is applied by the process described below. If desired, the electro ceramic coating  312  may also be applied to the interior surfaces of the valve bores  306  in the valve body  300 . 
         [0057]    Once again, the approximate thickness of the ceramic coating  312  is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but it may be thicker or thinner. Thin (0.005 to 0.006 mm.) and medium (0.010 to 0.012 mm.) thickness ceramic coatings  312  generally will not require secondary finishing for size or surface finish. Thicker ceramic coatings in the range of 0.020 to 0.050 mm. will generally require secondary surface finishing. The electro ceramic coating  312  on the valves  310  and bores  306  of the valve body  300  provides a more durable surface than bare aluminum, eliminates the galling potential existing when both surfaces are bare or untreated aluminum and, because of the surface porosity of the ceramic coating  312 , a small amount of oil (hydraulic fluid) is held in the interface between the valve  310  and valve body  300 , thereby reducing wear. 
         [0058]    Referring now to  FIG. 12 , a portion of a motor vehicle automatic transmission is illustrated and generally designated by the reference number  350 . The automatic transmission  350  includes a friction clutch pack  352  having interleaved friction plates  354  which are splined to an inner hub  356  and reaction plates  358  which are splined to an outer housing  362 . The inner hub  356  is coupled to and driven by a hollow shaft or quill  360 . The interleaved friction plates  354  and reaction plates  358  are disposed between a backing plate  364  which is splined to and rotates with the housing  362  and an apply plate  366  which is acted upon by a hydraulic actuator or operator  370 . The hydraulic actuator  370  is a balanced actuator and includes a circular aluminum piston  372  having an inner resilient seal  373 , a first, actuating chamber  374  on one side of the piston  372  and a second, compensating chamber  376  on the opposite side of the piston  372 . A first fluid passageway  378  selectively provides hydraulic fluid under pressure to the actuating chamber  372  and a second fluid passageway  382  provides hydraulic fluid to the compensating chamber  374 . 
         [0059]    An axially stationary complexly curved aluminum circular dam  384  having resilient seals  386  at its inner and outer edges seals the compensating chamber  376 . Disposed within the compensating chamber  376  is a circular spring  388  such as a Belleville spring or washer. The spring  388  engages or contacts an inner surface  392  of the piston  372  and a projecting surface  394  of the circular dam  384 . Since the spring  388  flexes as the piston  372  translates axially, these regions of contact are wear surfaces and are coated with an electro ceramic coating  396  applied in accordance with the process described below. The approximate thickness of the ceramic coating  396  is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but it may be thicker or thinner. The fabrication of the piston  372  and dam  384  of aluminum instead of steel reduces mass and inertia and contributes to improved vehicle fuel economy. 
         [0060]    Referring now to  FIG. 13 , a portion of an automatic transmission, similar to the automatic transmission  10  of  FIG. 1 , is illustrated and generally designated by the reference number  400 . The automatic transmission  400  includes a housing  402  which supports, locates and protects the internal components of the transmission  400  such as a hollow drive shaft or quill  404 , a plurality of friction clutch packs  406 , one of which is illustrated in  FIG. 13 , and a plurality of planetary gear assemblies  410 , one of which is also illustrated in  FIG. 13 . The planetary gear assembly  410  includes a sun gear  412 , a planet gear carrier  414  and a ring gear  416 . The planet gear carrier  414  is fabricated of aluminum and contains a plurality, typically three or four, planet gears  418  which are freely rotatably disposed on stub shafts  422  mounted in the planet gear carrier  414  and in constant mesh with both the sun gear  412  and the ring gear  416 . Because the planet gears  418  are helically cut, axial forces are generated as they rotate, thrust washers were often utilized between the planet gears  418  and the planet gear carrier  414 . An electro ceramic coating  426 , applied according to the process described below, is deposited on faces and shoulders  428  of the planet gear carrier  414  and adjacent and contacting surfaces of the planet gears  418 . Additionally, at castle or spline connections  430  between the planet gear carrier  414  and a hub  432  which is coupled to an element such as the outer housing  434  of the planetary gear assembly  406 , the engaging faces and preferably sides of the castle or spline connections  430  are coated with the electro ceramic coating  426  applied as described below. On both the faces and shoulders  428  of the planet gear carrier  414 , as well as the castle or spline connections  430 , the approximate thickness of the electro ceramic coating  426  is 0.005 to 0.050 mm. (0.000197 to 0.00197 inches) but it may be thicker or thinner. 
         [0061]    Referring now to  FIG. 14 , with regard to all of the above delineated aluminum components, the overall process  500  and the individual steps involved in applying the electro ceramic coating will now be described. First, in a step  502  the surface or surfaces of the component are cleaned with a degreasing solution to removes an oils or foreign substances that would interfere with the electro coating process. Next, in a step  504 , the component undergoes a first water rinse to remove the degreasing solution. In an optional second rinse step  506 , the component may be rinsed with deionized water. 
         [0062]    The ceramic coating is applied in a step  510 . In the step  510 , low voltage direct current is utilized in a plating bath wherein the negative pole is connected to a plate (cathode) submerged in the bath and the positive pole is connected to the aluminum component (anode) to be coated. Preferably, the liquid plating bath has a pH of 2.5 and includes dispersed titanium (Ti). A plasma electrolytic deposition process, typically taking between one and five minutes to achieve the above-stated thickness (0.005 to 0.050 mm.), then occurs in which negative titanium ions acquire O 2  molecules and form a coating of titanium dioxide on the surface or surfaces of the component. Typical hardness of such a coating is between 300 and 1400 Hv. 
         [0063]    As stated above, the resulting ceramic coating is porous and thus may contain lubricating oil or air which improves component life and operation and reduces sliding friction. After the desired thickness of the ceramic (titanium dioxide) coating has been achieved, the component is removed from the plating bath and rinsed in a step  512 . A final step  514  involves drying the component which is then ready for inventorying or movement to a production line. 
         [0064]    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.

Technology Classification (CPC): 5