Abstract:
The present disclosure relates to a dry-clutch transmission having various cooling techniques. Some techniques include forming different structural features on transmission components so as to create an organized air flow. The disclosed techniques are applicable to both opened and closed transmission housings.

Description:
TECHNICAL FIELD 
     The present disclosure relates to dry-clutch transmissions with various heat transfer techniques including clutch or plate features that promote an organized air flow. 
     BACKGROUND 
     Conventional vehicle transmissions predominantly employ wet clutches to accomplish gear shifting. Transmissions typically include a transmission fluid which is recycled throughout the transmission. Wet clutches generally provide greater heat transfer and temperature control than dry clutches. Wet clutches also, however, have a lower coefficient of friction than dry clutches. Wet clutches are further known to slip pre-engagement. 
     Dry clutches tend to provide higher coefficients of friction than wet clutches. Dry clutches can provide lower costs and complexity. Still, dry clutches can have thermal management issues. For example, dry clutches can reach higher temperatures in repeat vehicle launch events with heavy vehicle load and road grade conditions. Some existing designs have attempted to reduce transmission heating in wet clutch transmission. U.S. Pat. No. 6,568,518 titled “Clutch for a Power Train of a Motor Vehicle” discloses a clutch having fan blades configured to generate an air stream over the surface of the flywheel. The blades disclosed are flowing in a single direction which produces a relatively undisturbed fluid flow path. A more viscous flow would yield greater heat transfer. 
     Therefore, it is desirable to have a dry-clutch transmission with improved heat transfer techniques. 
     SUMMARY 
     The present invention may address one or more of the above-mentioned issues. Other features and/or advantages may become apparent from the description which follows. 
     Certain embodiments of the present invention regard a dry-clutch transmission, including: a first plate having a plurality of blades formed therein. At least one of the plurality of blades is positioned in a different direction than the other blades. 
     Another exemplary embodiment of the present invention involves a dry-clutch transmission with cooling system, the system including: a drive plate having a plurality of blades formed therein; and a transmission component having a conduit configured to guide air away from a center of the transmission. 
     Another exemplary embodiment of the present invention regards a method of cooling a vehicle powertrain through generating an organized flow pattern with respect to the powertrain, the method including: providing a first conduit formed in a drive plate, the first conduit configured to pull air towards the center of the transmission; providing a second conduit on the drive plate, the second conduit configured to exhaust air away from the center of the transmission; pumping air through the transmission; and guiding air toward the outside of the transmission housing. 
     Yet another embodiment of the present invention regards a method of cooling a powertrain, the method including the step of: forming a plurality of ribs on a cylinder block; and flowing engine coolant through the cylinder block. 
     One advantage of the present teachings is that they provide a relatively lower cost design than a wet clutch transmission with significant heat reduction capabilities. Transmission durability is enhanced with implementation of the cooling systems. 
     Another significant advantage of the present teachings is that they provide a less complex transmission than a wet clutch transmission with significant heat reduction techniques. Some of the disclosed cooling techniques generate an organized flow within the transmission housing without requiring an external fan for cooling. 
     In the following description, certain aspects and embodiments will become evident. It should be understood that the invention, in its broadest sense, could be practiced without having one or more features of these aspects and embodiments. It should be understood that these aspects and embodiments are merely exemplary and explanatory and are not restrictive of the invention. 
     The invention will be explained in greater detail below by way of example with reference to the figures, in which the same references numbers are used in the figures for identical or essentially identical elements. The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. In the figures: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side, partial cross-sectional view of an engine and dry-clutch transmission with organized flow according to an exemplary embodiment of the present invention. 
         FIG. 2  is an exploded view of a dry-clutch assembly compatible with the transmission of  FIG. 1 . 
         FIG. 3  is a perspective view of the clutch drive plate of  FIG. 2 . 
         FIG. 4  is a front view of the drive plate of  FIG. 3 . 
         FIG. 5  is a cross-sectional view of the drive plate of  FIG. 3  along line  5 - 5 . 
         FIG. 6  is a cross-sectional view of the drive plate of  FIG. 3  along line  6 - 6 . 
         FIG. 7  is a side view of a drive plate with blades according to another exemplary embodiment. 
         FIG. 8  is a side view of the drive plate and blades of  FIG. 7 . 
         FIG. 9  is a front view of the clutch cover of  FIG. 2 . 
         FIG. 10  is a side view of the clutch cover of  FIG. 2 . 
         FIG. 11  a perspective view of the clutch pressure plate of  FIG. 2 . 
         FIG. 12  is a front view of the clutch pressure plate of  FIG. 2 . 
         FIG. 13  is a front view of the flywheel of  FIG. 2 . 
         FIG. 14  is a perspective view of the flywheel of  FIG. 2 . 
         FIG. 15  is a rear view of the engine cylinder block and oil pan of  FIG. 2 . 
     
    
    
     Although the following detailed description makes reference to illustrative embodiments, many alternatives, modifications, and variations thereof will be apparent to those skilled in the art. Accordingly, it is intended that the claimed subject matter be viewed broadly. 
     DETAILED DESCRIPTION 
     Referring to the drawings wherein like characters represent the same or corresponding parts throughout the several views there are shown exemplary dry-clutch transmissions with cooling techniques that provide improved heat transfer. Several design features are incorporated into components of the transmission in order to generate an organized flow of air in the transmission housing. Some exemplary design features include using fan blades on a drive plate positioned in opposing directions. Radial and axial apertures are placed in a pressure plate and flywheel to exhaust air away from a center of the transmission and reduce clutch heat in the housing. Ribbing is also included on the engine block and oil pan to improve convective heat transfer from the transmission housing to the engine coolant. Some or all of these features can work in concert to create an organized flow and improve heat transfer from the transmission clutch. 
     Referring now to  FIG. 1 , there is shown therein a powertrain  10  for use in a vehicle. The powertrain  10  includes an internal combustion engine  20 . The engine illustrated is an inline four cylinder engine. A radiator  15  is positioned at the front of the engine. An oil sump (or pan)  30  which holds the engine&#39;s oil reserves is at the base of the engine. The oil  40  is cycled through the engine to lubricate engine bearings. The block  50  is attached to a transmission  60  through a crankshaft (not shown). The transmission has a housing  70  that rests flush against the cylinder block  50 . In this embodiment, the engine block  50  includes a series of ribs  80  (or beads) formed on the outer surface of the block and the oil pan  30 . The ribs  80  increase the surface area in which engine oil, coolant and/or air engage thus generating more heat transfer at the upper-rear and lower-rear portions of the engine. In this manner, heat is transferred from an input clutch  65  where the clutch is running warmer than the engine. 
     The transmission  60 , of  FIG. 1 , is a dry-clutch transmission. The transmission  60  can be any manual, automatic, continuously-variable or electrically-variable transmission. In this embodiment, the transmission is a dual-clutch automatic transmission.  FIG. 1  conveys an exemplary organized air flow  100  in the forward portion of the transmission housing  70  where the input clutch  65  is positioned. On the engine side, heat travels from clutch  65  to the engine block  50  and bell housing, engine oil and coolant to the radiator and is dispensed into ambient. In this embodiment, the transmission  60  is a closed system; air is not taken into or exhausted out of the transmission. In other embodiments, the transmission is an open system; ambient air is filtered into the transmission and exhausted therefrom. Referring back to the embodiment shown in  FIG. 1 , the air flow  100  includes two primary streams. Air is forced away from the center of the transmission, C. During engine operation, various clutch features work in concert with the angular momentum of clutch components to support this air stream  100  as shown in the examples below. The second stream cycles air from the outer diameter of the transmission (or transmission housing  70 ) toward the center of the transmission, C. Various clutch features work in concert with the angular momentum of clutch components to support this air stream as shown in the examples below. 
     Referring now to  FIG. 2 , there is shown therein an exploded view of an exemplary clutch assembly compatible with the transmission  60  of  FIG. 1 . The transmission includes a cooling system  105 . Each of the four components in the system  105  include structural features that guide air in the direction of the organized flow path  100  partially shown in  FIG. 1 . Each component includes a series of conduits that direct air in the predetermined flow path. A drive plate  200  is in the most forward position of the transmission. Drive plate  200  includes two sets of blades  210  and  220 —one set proximate to the outer diameter of the plate face ( 210 ) and another set proximate to the inner diameter of the plate face ( 220 ). Blades  210  are positioned in a different direction than blades  220 . Blades  210  are oriented to receive air in a clockwise direction from a transmission-to-engine perspective—the X-axis as shown in  FIG. 2 ; blades  220  are oriented to receive air in a counterclockwise direction. Blades  220  direct air toward the clutch center. Blades  210  direct air away from the clutch center or toward the outer diameter of the clutch. 
     A clutch cover  230  is also included in the assembly of  FIG. 2 . The clutch cover  230  includes a series of apertures  240  along the perimeter of the cover. The apertures  240  enable ingress and/or egress of air from the assembly. A pressure plate  250  nests concentrically within the clutch cover  230 . Pressure plate  250  includes various channels  260  that extend radially with respect to the pressure plate. Air is guided out toward the outer diameter of the pressure plate  250 . A flywheel plate  270  is also concentrically aligned with the other members of the clutch assembly. Clutch plates (not shown) are assembled between the pressure plate  250  and flywheel plate  270 . Flywheel plate  270  includes radial channels  280  that guide air toward the outer diameter of the flywheel plate. 
     Giving particular attention in the drive plate  200 , as shown in  FIGS. 3-4 , the drive plate has two sets of blades  210  and  220  that act as conduits for air. Blades  210  are proximate the outer diameter of the drive plate. In this embodiment, six blades are included in the first set of blades. Blades  210  are positioned 60 degrees apart with respect to each other. Blades  210  are configured to direct air away from the clutch center or toward the outer diameter of the clutch. Each blade includes a flange edge  300  bent at a predetermined angle. In this embodiment, the flanges  300  are bent at an angle of 30 degrees. Drive plate  200  includes perforations  310  to support the extension of the blades  210  and  220  from drive plate. An outline of the blades  210  and  220  are cut into the drive plate  200 . Drive plate  200  also includes two semi-circular apertures  320  to alleviate stress in at the corners of the blades. 
     Blades  220 , as shown in  FIGS. 3-4 , are positioned in a different direction than blades  210 . Blades  220  act as a conduit for air and are oriented to direct air toward the clutch center. Blades  220  are proximate the inner diameter of the drive plate  200 . In this embodiment, eight blades are included in the second set of blades. Blades  220  are positioned 45 degrees apart with respect to each other. Each blade includes a flange edge  300  bent at a predetermined angle. The opposing directions of blades  210  and  220 , respectively, create a more turbulent flow path between the clutch  65 , bell housing  70 , cylinder block  50  and oil pan  30  (as shown in  FIG. 1 ). 
       FIGS. 5 and 6  illustrated the opposing orientation of blades  220  and  210 , respectively.  FIG. 5  illustrates a cross-sectional view of the drive plate  200  of  FIG. 3  along line  5 - 5 . Each blade  210 ,  220  is angled towards the engine cylinder block  50  (as shown in  FIG. 1 ). A blade from blade set  220  is show in  FIG. 5 . Blade  220  is angled approximately 30 degrees counterclockwise from the drive plate surface  330 .  FIG. 6  illustrates a cross-section view of the drive plate of  FIG. 3  along line  6 - 6 . A blade from blade set  210  is show therein. Blade  210  is angled approximately 30 degrees clockwise from the drive plate surface  330 . 
     Drive plate  200  is stamped. Blades  210 ,  220  are manufactured from secondary manufacturing operations such as cutting and stamping. The disclosed drive plate is composed of steel. 
     In another embodiment, as shown in  FIGS. 7-8 , drive plate  400  (as partially illustrated) has a bi-metal composition.  FIGS. 7 and 8  are side views of a drive plate  400  with blades  410  and  420  adhered together with a bonding material  415 . The body of drive plate  430  is composed of a different material than the blades  410  and  420 . As shown in the figures, blades  410  and  420  are attached to the drive plate  400  using a fastener  440 . In this case, the fastener  440  is a rivet. Other fasteners can be used such as, for example, welds, nuts and bolts, clamps or screws. Blades  410  and  420  have shape memory. Blades  410  and  420  are pre-torqued with respect to the drive plate body  430 , as shown in  FIG. 8 . Blades  410  and  420  are thermally actuable. Once the transmission reaches a predetermined threshold—T Threshold , blades  410 ,  420  bend with respect to the plate body  430 . At room temperature, blades  410  and  420  are flat with respect to the body of the drive plate  430 . In one embodiment, the threshold temperature for the blades is 200 degrees Celsius. As the temperature increases the blades  410 ,  420  raise. In this embodiment, the maximum deformation of blades  410  and  420  is seen at  200  degrees Celsius. In another embodiment, the threshold temperature for the blades is 100 degrees Celsius. The threshold temperature for blades  410 ,  420  can be set according to system cooling targets. Different materials can be used to accomplish thermal actuation at a desired temperature. In the illustrated embodiment, blade  410  is composed of an aluminum material and blade  420  is composed of steel. Exemplary combinations for the bi-metal drive plates blades include steel-aluminum, steel-copper, steel-tin, aluminum-aluminum, aluminum-tin, and aluminum-copper. Other material combinations, such as those including titanium or magnesium, will be appreciated by an ordinary artisan. 
     Referring now to  FIGS. 9-10 , there is shown therein the clutch cover  230  of  FIG. 2 . Clutch cover  230  partially covers or encases the clutch assembly. Cover  230  can be secured to the drive plate  200  (as shown in  FIG. 2 ). In one embodiment, cover  230  is bolted onto the drive plate. Cover  230  includes a series of conduits  240  enabling air to flow out of the clutch assembly—apertures  240  are formed in the outer perimeter of the clutch cover. Apertures  240  work in concert with other clutch features to guide air from the input shaft of the transmission to the housing. In this embodiment, apertures  240  are roughly ½″ in diameter. Apertures  240  can be of varying sizes. Apertures  240  can be formed using any number of techniques. Apertures  240  can be machined into the cover. In one embodiment, apertures  240  are molded into the cover  230 . Cover  230  is composed of stamped steel in this embodiment. Cover  230  can be composed of any number of materials including aluminum, magnesium or cast iron. 
     Referring now to  FIGS. 11 and 12 , there is shown therein the pressure plate  250  of  FIG. 2 . Pressure plate  250  nests inside of clutch cover  230  of  FIG. 2 . Pressure plate  250  is affixed to the drive plate  200  and clutch cover  230 . In this embodiment, pressure plate  250  is bolted onto the assembly at  500 . Pressure plate  250  includes a series of conduits  260  enabling air to flow out of the clutch assembly—radial channels  260  formed in the outer perimeter of the pressure plate  250 . As shown in  FIG. 12 , pressure plate  250  has 24 channels  260 . Channels  260  work in concert with other clutch features to guide air from the input shaft of the transmission to the housing. In this embodiment, channels  260  are roughly one eighth inch in diameter. Channels  260  can be of varying sizes. Channels  260  can be formed using any number of techniques. In the illustrated embodiment, channels  260  are machined into the pressure plate  250 . In one embodiment, the grooves are molded into the pressure plate  250  and the channels  260  are machined into the plate in a secondary process. Channels  260  are formed of cast iron in this embodiment. Pressure plate  250  can be composed of any number of materials including aluminum, magnesium or steel. 
     Now with reference to  FIGS. 13 and 14 , there is shown therein the flywheel plate  270  of  FIG. 2 . Flywheel is driven from a clutch cover (e.g.,  230  as shown in  FIG. 2 ) which is attached to the drive plate  200 . A clutch plate, not shown, is positioned between the pressure plate  250  and flywheel plate  270 . Flywheel plate  270  is arranged concentrically adjacent the pressure plate  250 . Flywheel  270  is fixed to a second drive plate (not shown). Flywheel plate  270 —as shown in FIGS.  13 - 14 —attaches to the drive plate  200  through apertures  550 . Flywheel plate  270  includes a series of conduits  280  enabling air to flow out of the clutch assembly; channels  280  are formed on in the outer perimeter of the flywheel plate  270 . Channels  280  are formed in varying directions with respect to the radius of the flywheel plate  270 . Four channels  280  are radially aligned. Channels  280  can be formed in avoidance of other structural features of the plate. For example, channel  560  is not radially aligned with the flywheel plate  270  but formed at an obtuse angle with respect to the radius of the plate. In this manner, channel  560  enables sufficient egress of air from the inner diameter of the flywheel without compromising the structural rigidity of flanges  570 . 
     Flywheel plate  270 , as shown in  FIG. 14 , includes 11 channels. Channels  280  work in concert with other clutch features to guide air from the input shaft of the transmission to the housing. In this embodiment, channels  280  are roughly one eighth inch in diameter. Channels  280  can be of varying sizes. Channels  280  can be formed using any number of techniques. In the illustrated embodiment, channels are machined into the flywheel plate  270 . In one embodiment, the channels  280  are molded into the flywheel plate  270 . In the illustrated embodiment, channels are machined into the plate in a secondary process. Channels  280  are cast in. Flywheel plate  270  can be composed of any number of materials including iron, steel, magnesium or aluminum. In the illustrated embodiments, flywheel plate  270  is die cast. 
     Referring now to  FIG. 15 , the features incorporated on the engine block  50  that assist in thermal transfer from the transmission  60  (as shown in  FIG. 1 ) are illustrated. Engine block  50  includes ribbing on the water jacket area of the block  50  outside the housing to improve heat transfer from the transmission housing air to the engine coolant system and vehicle radiator. A rear view of the engine bell housing  600  of  FIG. 1  is shown in  FIG. 15 . The upper portion of the engine bell housing  600  includes a series of ribs  610  (or beads) on the outer surface of the housing. Ribs  610  consist of lateral protrusions formed into the engine bell housing. Ribs  610  are adjacent the cylinder block  50  and configured to promote greater heat transfer during operation by increasing the surface area that engine fluid contacts. A similar set of ribs  620  are incorporated onto the engine bell housing  600  at the base or bottom of the housing or oil pan  30 . Ribs  620  are also formed in the outer surface of the oil pan  30 . Ribs  620  are adjacent the oil sump or oil pan  30  and configured to enable greater heat transfer from a transmission input clutch. Ribs  610  and  620  improve the clutch-to-engine thermal transfer through convective cooling. 
     In the illustrated embodiment of  FIG. 15 , ribs  610 ,  620  are formed within the engine bell housing  600 . Ribs  610 ,  620  are molded into the housing  600 . In other embodiments, ribs  610 ,  620  are machined out of the housing; ribs are formed as recesses in the inner surface of the housing. Engine housing is composed of aluminum. Other feasible design materials can include cast iron or magnesium. 
     Also disclosed is an exemplary method of cooling a vehicle powertrain through generating an organized flow pattern (e.g., as shown in  FIG. 2 ) with respect to the powertrain. The method includes the step of providing a first conduit formed in a drive plate, the first conduit configured to pull air towards the center of the transmission. Blades  220  formed on the drive plate of  FIGS. 3-4  pull air towards the center of the transmission. The method includes providing a second conduit on the drive plate, the second conduit configured to exhaust air away from the perimeter of the clutch. Blades  210 —faced in an opposing direction to blades  220 —are configured to exhaust air away from the center of the transmission. The method also includes pumping air through the transmission; and guiding air toward the outside of the transmission housing. 
     Another method of cooling a powertrain is taught herein. The method includes the step of: forming a plurality of ribs on a cylinder block. The ribs are configured to cause turbulence in engine fluid flow. Exemplary ribs  610 ,  620  are shown in  FIG. 15 . The method also includes flowing engine coolant through the cylinder block. Ribs increase the surface area engine fluid contacts thus enabling greater heat transfer from the transmission. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the methodologies of the present invention without departing from the scope its teachings. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.