Patent Publication Number: US-2015075941-A1

Title: Transmission with durability enhancement techniques

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation and claims the benefit of U.S. non-provisional patent application Ser. No. 12/896,877, filed Oct. 2, 2010, which is a continuation-in-part and claims the benefit of U.S. Non-Provisional Patent Application Ser. No. 12/265,283 titled “Temperature Control of Dual Input Clutch Transmission” filed Nov. 5, 2008. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to durability enhancement techniques for a dry-clutch vehicle transmission. 
     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 as wet clutches have a lower coefficient of friction. 
     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 and durability issues. Some powershift dry dual-clutch transmissions (or “DCTs”) comprise a manual clutch construction, e.g., as disclosed in U.S. Patent Publication No. 2010/0113216 titled “Temperature Control of Dual Input Clutch Transmission.” Two clutches are utilized to provide functionality closer to that of an automatic transmission clutch vehicle launch. Temperature can significantly impact the length of service life of a transmission in which each input clutch is a dry clutch. A friction surface—the primary source of heat for the transmission—is surrounded by material and lacks a direct convection path for cooling. The transmission has heavy components with high inertia and low heat dissipation. Though the use of a controlled fan can improve cooling in the transmission, the indirect air flow path from the fan to the heat source slows down the cooling process. 
     Another common issue in dry-clutch transmissions is that clutch wear can be significantly increased by high operating temperatures. Repetitive engagement of clutch components can cause wear on the friction plate. This wear can decrease clutch lifespan. Some existing transmissions have a clutch adjustment mechanism that iteratively adjusts the position of the pressure plate when the clutch becomes slow to engage. Once a maximum distance for clutch engagement is detected the system moves clutch components into a tighter relative position. Since the adjustment is stepwise, the system repetitively over- and under-adjusts both after adjustment and before re-adjustment, respectively. A more efficient method of clutch adjustment is desired. Additionally, a more robust and reversible design is preferred. 
     Therefore, it is desirable to have a dry-clutch transmission with improved durability and wear reduction techniques. Cooling techniques which provide a more direct convection and conductive path are needed to reduce overheating in the transmission. Moreover, a continuously variable clutch wear compensation assembly is desirable to have a more flexible yet, effective and robust clutch wear adjustment mechanism. 
     SUMMARY 
     The present invention addresses at least 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 relate to a dry-clutch transmission, having: a clutch assembly; and a cooling system, including: a hub onto which the clutch assembly is journaled, the hub having a plurality of apertures directed toward friction surfaces in the clutch assembly; a fan configured to direct air through the hub; and a controller configured to control the fan according to a clutch temperature. 
     Another exemplary embodiment of the present invention relates to a dry-clutch transmission, including: a clutch assembly; and a divider plate included in the clutch assembly having a plurality of airfoil ribs formed on a surface of the plate. A leading edge of at least one of the airfoil ribs is aligned within 60 degrees of a relative vector equal to the sum of an air speed vector and a clutch speed vector. 
     Another exemplary embodiment of the present invention relates to a dry-clutch transmission, with: a clutch assembly having a pressure plate; and a clutch compensation assembly including: an electric motor; a cam interface between the pressure plate and motor, the motor configured to move the cam interface; and a controller configured to control the electric motor. 
     Another exemplary embodiment of the present invention relates to a clutch compensation assembly, having: an actuator configured to continuously adjust the position of a clutch pressure plate on an as-needed basis. 
     Yet another exemplary embodiment of the present invention relates to a transmission control unit, having: fan control logic configured to control a fan according to an inferred clutch temperature; and clutch wear compensation logic configured to adjust clutch pressure plate position according to a clutch actuation condition. 
     One advantage of the present disclosure is that it teaches cooling techniques that force flow close to the friction surface—a primary source of heat for the transmission—in order to reduce temperature response time to heat events. In some embodiments, the hub includes nozzles of various sizes to force more air towards hotter plates (e.g., friction plates located in the middle of the clutch pack). 
     Another advantage of the present disclosure is that it teaches a cooling system having inlet and outlet air thermostats giving feedback for software error reduction (such as inferred temperatures) and thermal model reset. This information yields improved shift and launch feel for better clutch torque accuracy through reduced coefficient of friction variation and avoidance of higher temperature levels. 
     Another advantage of the present teachings is that they enable a dry-clutch transmission to run a longer cooling duty cycle than cooling oil. The cooling duty cycle is improved because the fan is used on-demand which can increase energy and fuel efficiency. 
     Another advantage of the present disclosure is that it teaches the use of spacers shaped like airfoils aligned with relative air velocity to assist flow thus further contributing to clutch cooling. 
     Yet another benefit of the present disclosure is that the continuously variable, electric wear adjustment assemblies taught are more robust than a mechanical or iterative system. Moreover the continuously variable system is reversible for error correction enabling better clutch torque accuracy and efficiency during engagement. 
     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 schematic depiction of a dry-clutch vehicle transmission. 
         FIG. 2  is a side view of a transmission clutch assembly with an exemplary cooling system. 
         FIG. 3  is a cross-sectional view of a hub in the clutch assembly of  FIG. 2 . 
         FIG. 4  is a front view of a divider plate in the clutch assembly of  FIG. 2 . 
         FIG. 5  is a partial cut-away of the divider plate of  FIG. 4 . 
         FIG. 6  is a side view of a clutch wear compensation assembly according to an exemplary embodiment of the present invention(s). 
         FIG. 7  is a cross-sectional view of a cam interface in the clutch wear compensation assembly of  FIG. 6  through line  7 - 7 . 
         FIG. 8  is a top view of the cam interface of  FIGS. 6 and 7 . 
         FIG. 9  is a side view of a clutch wear compensation assembly according to another exemplary embodiment of the present invention(s). 
         FIG. 10  is a top view of a cam interface in the clutch wear compensation assembly of  FIG. 9 . 
         FIG. 11  is a graph of the adjustment logic of a clutch wear compensation assembly according to an exemplary embodiment of the present invention(s). 
         FIG. 12  is transmission control unit according to an exemplary embodiment of the present invention(s). 
         FIG. 13  illustrates an exemplary method of operating a transmission cooling fan. 
         FIG. 14  illustrates an exemplary method of controlling a clutch compensation assembly for a vehicle transmission. 
     
    
    
     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 various exemplary systems for reducing transmission wear and enhancing transmission durability. The systems are best appreciated in a powershift dry dual-clutch transmissions (or “DCTs”) where cooling and wear can be significant issues for the transmission. Though the illustrated examples regard powershift DCTs, the present teachings can be implemented on different kinds of vehicle transmissions including, but not limited to, single-clutch manual transmissions, automatic transmissions, or wet-clutch transmissions. A cooling system is provided that enables a more direct cooling path to the clutch surface thus improving fan efficiency and reducing cooling response time. The fan helps in achieving a more concentrated, forced flow improving heat transfer. This is accomplished, in part, by running the air as close as possible to the heat source (i.e., the friction surfaces in the clutch assembly). The fan is linked to a controller that is responsive to transmission temperatures. Multiple thermocouples are dispersed throughout the transmission to give feedback to the fan controller as to the thermal conditions of the transmission during operation. 
     Some of the disclosed techniques also improve transmission durability through the implementation of a continuously variable clutch compensation assembly. Instead of iterative adjustments of clutch components, the system continuously adjusts clutch components as-needed. Adjustments are reversible. 
     Referring now to  FIG. 1 , there is shown therein a schematic depiction of a vehicle transmission  10 . The transmission  10  is a dual dry-clutch powershift transmission having a first dry input clutch assembly  20  that selectively connects an input  30  of transmission  10  to gears in set  40  associated with a first layshaft  50  and a second dry input clutch assembly  60 . The second dry input clutch assembly  60  selectively connects to the gears in set  70  associated with a second layshaft  80 . In the illustrated embodiment, input  30  is driveably connected to a power source such as an internal combustion engine or an electric motor. An electronic transmission control unit (or “TCU”) controls the input clutch assemblies  20 ,  60  through command signals sent to an electric motor that actuates the input clutches. Different gear ratios can be accomplished through the manipulation of the dual input clutches and gear selection actuators. An output shaft is connected to a vehicle driveline to effectuate the different modes of operation or shift gears for the transmission. The two input clutch assemblies  20 ,  60  provide functionality similar to that of an automatic transmission. The transmission can see higher temperatures since each input clutch assembly  20 ,  60  is a dry clutch. 
     The transmission  10 , of  FIG. 1 , includes a cooling system  90 . The cooling system  90  includes a motor-driven fan  100 . Fan is connected to a motor  110  that is controlled by the transmission control unit  120 . The control unit  120  selectively supplies power to the fan motor  110  to increase or decrease fan speed. Fan speed can be decreased to zero or adjusted to rotate in a different direction than the default direction. When the fan  100  is operated in an opposing direction the fan is said to have a negative speed. The TCU  120  is linked to an electrical power source  130  (e.g., the vehicle battery or a fuel cell). Fan  100  is positioned so as to provide air more directly onto the friction surfaces of the input clutch assemblies  20  and  60  (as discussed in detail with respect to  FIGS. 2 and 3 ) through apertures in a hub onto which the clutches are journaled. In this manner, fan  100  is in direct fluid communication with input clutch surface  140  and input clutch surface  150 . 
     Now with reference to  FIGS. 2 and 3 , there is shown therein a side view of the input clutch assembly  20  with the cooling system  90  of  FIG. 1 . The clutch assembly  20  shown includes a series of friction plates  200  sandwiched between two pressure plates  210  (or drive plates). Each friction plate  200  has at least one friction surface (e.g.,  140 ) that enables collective engagement when a clutch actuator applies pressure to the pressure plate(s). Friction surfaces are the primary source of heat during transmission operation, especially during launch. 
     Clutch assembly  20 , as shown in  FIG. 2 , is journaled onto a hub  230 . Hub  230  is configured to be concentric with an input shaft (e.g. layshaft  50  as shown in  FIG. 1 ). Hub  230  includes a plurality of radial apertures  240  interspersed between clutch assembly components. In this embodiment, the apertures  240  are aligned with the friction surfaces of the friction plates. Fan  100  is in direct fluid communication with clutch surfaces. A fluid path is defined in the hub  230 . Air is directed through the interior of hub  230 , out of apertures  240  and directly onto friction surfaces. Air flows out of the outer diameter of the clutch assembly  20  and exhausted out of the transmission housing. 
     Fan speed can be increased and decreased according to predetermined conditions. Fan  100  is linked to the electric motor  110  and controller  120  as shown in  FIGS. 1 and 2 . Controller  120  is configured to selectively control the fan  100  according to a measured or inferred clutch temperature. Controller  120  sends a warning signal to a user interface  250  if the measured or inferred clutch temperatures exceed a predetermined threshold. In one embodiment, the threshold is 300 degrees Celsius. 
     Two thermocouples  260  and  270  are positioned in the transmission, as shown in  FIG. 2 . Thermocouples  260 ,  270  are hard-wired or linked to controller  120 . Thermocouples  260 ,  270  provide temperature readings at various locations in the transmission. In this embodiment, thermocouple  260  is positioned upstream of the clutch assembly  20 . Thermocouple  260  is configured to read the temperature of air entering the hub  230  and clutch assembly  20 . Thermocouple  270  is positioned at the outer diameter of the clutch assembly  20  and is configured to take temperature readings at the outlet of the clutch assembly. Thermocouples  260 ,  270 —positioned in air inlet and discharge, respectively—can produce data used for the following purposes: 1) performing temperature integration (exposure) for quantifying usage severity; 2) improving thermal model accuracy by monitoring error and resetting if needed; and 3) detecting insufficient air flow rates. Controller  120  is programmed with predetermined clutch temperature thresholds for increasing and decreasing fan speed. Controller  120  includes fan control logic configured to control the fan according to an inferred or measured clutch temperature (as is discussed in more detail herein below with respect to  FIG. 13 ). 
     The cooling system  90 , as particularly shown in  FIG. 3 , includes differently sized apertures  240  in the hub  230  on which the clutch assembly is journaled onto. Hub  230  includes five apertures. Aperture  300  is sized larger than apertures  310 ,  320 ,  330  and  340 . Aperture  300  enables more flow to reach the center of the clutch assembly  20 , where higher temperatures are experienced. Apertures  310  and  340  are smaller than apertures  300 ,  320  and  330 . Each aperture  300 ,  310 ,  320 ,  330  and  340  (or nozzle) has an axial dimension—in the longitudinal direction of the hub—and a radial dimension, perpendicular to the axial direction. Each aperture  300 ,  310 ,  320 ,  330  and  340  is an arc-shaped slot formed in the body of hub. Apertures  300 ,  310 ,  320 ,  330  and  340  can also have varying lengths to yield different cooling effects on the clutch assembly. Apertures can be, for example, die cast, machined or stamped out of the hub  230 . In one embodiment, the mold for hub  230  includes protrusions to create apertures in shell of the hub. Hub  230  can be any stationary or rotating transmission component. Hub can be splined onto an input shaft, output shaft or hub can represent the input/output shafts. In another embodiment, hub  230  partially encases the clutch assembly so that hub is at the outer diameter of the clutch assembly. Air is passed through the hub and onto the outer diameter of the clutch assembly. 
     The clutch assembly  20  further includes a series of separator or divider plates  400 , as shown in  FIGS. 4 and 5 . Divider plate  400  includes airfoil ribs  410  that also improve air flow from the inner diameter of the transmission to the outer diameter of the transmission. In this manner, greater cooling is achieved. In  FIGS. 4 and 5 , the separator or divider plate  400  of  FIG. 2  is shown from line  4 - 4 . In order to assist rotation and facilitate flow, the separating surfaces of the plate  400  are shaped with an airfoil. The front view of divider plate  400  illustrates airfoil ribs  410  formed on the face of the plate. As shown in  FIG. 5 , airfoil ribs  410  are particularly positioned with respect to the rotational momentum of the clutch and the direction of airflow, from the inner diameter of the clutch to the outer diameter of the clutch. Airfoil ribs  410  decrease the resistance to air flow while the divider plate is rotating. The air entering the clutch assembly is directed radially outward from the clutch assembly. The air flow defines an air speed vector (V Air ) in line with the radius of the divider plate. The rotation of the clutch also defines a vector by which the components on the face of the divider plate travel. The clutch speed vector (V Clutch ) in this embodiment is normal to the air speed vector. Airfoil ribs  410  are positioned so that the leading edge of the airfoil rib  420  is aligned with a relative vector (V Rel ) equal to the sum of the air speed vector and clutch speed vector. In the illustrated embodiment, the relative vector V Rel  is approximately 45 degrees from V Clutch . In another embodiment, the leading edge of the airfoil rib  420  is positioned 15 degrees from the relative vector. The leading edge of the airfoil rib  420  can be positioned within +/−60 degrees of the relative vector, V Rel . The relative vector can be larger or smaller depending on the air flow path and direction of clutch rotation. 
     Referring now to  FIGS. 6 through 8 , there is shown therein an exemplary continuously variable clutch wear compensation assembly  500 . The clutch compensation assembly  500  is continuously variable in that the assembly can adjust the axial position of a pressure plate  510  in a manner directly proportional to the displacement caused by clutch wear. Compensation assembly  500  is electrically controlled by a servo motor  520  that provides power in either direction so that the clutch compensation assembly&#39;s adjustments are reversible. A clutch assembly  530  is shown in  FIG. 6  with an exemplary clutch compensation assembly attached thereto. Motor  520  is linked to a controller  540  (e.g., the transmission control unit as discussed with respect to  FIG. 1 ). The motor and controller act as an actuator  550  for the clutch compensation control assembly  500 . Controller  540  is configured to control adjustment of the compensation assembly according to predetermined conditions. One predetermined condition is the distance to clutch engagement. The compensation assembly includes a position sensor  560  placed with respect to the clutch assembly  530 . The compensation assembly  500  is configured to adjust the pressure plate  510  according to a clutch actuation condition. In this embodiment, the clutch actuation condition is distance to clutch engagement. Position sensor  560  detects how much displacement must occur in the clutch assembly  530  before the clutch is fully or substantially engaged. Position sensor  560  is shown linked to a second pressure plate  570 . Position sensor  560  can also be placed in the inner diameter of the clutch assembly  530 , at an end of the other pressure plate  510  or in another location. Position sensor  560 , in this embodiment, is wirelessly connected to the controller  540 . A clutch actuator (not shown) is used to move at least one of the two pressure plates  510 ,  570  together to cause engagement of the clutch. 
     The clutch compensation assembly  500 , of  FIG. 6 , comprises a cam interface  580  that enables the assembly to continuously adjust the position of pressure plate  510 . Cam interface  580  includes two matable, ramped surfaces having complementary angles—as also shown in  FIGS. 7 and 8 . Surface  590  is coupled to plate  610 . On the opposite side of plate  610 , a gear teeth  620  engages a gear  630  linked to the servo motor  520  (as shown in  FIG. 6 ). Bushings  640  are included in this embodiment to facilitate the rotation of plate  610  and shaft  650  that extends between the motor  520  and gear  630 . Mating surface  600  is coupled to pressure plate  510 . As shown in  FIG. 8 , as plate  610  is rotated with respect to the inner diameter of the transmission, pressure plate  510  is moved axially forward with respect to the transmission. Each ramped surface  600 ,  590  is angled approximately 20 degrees from the pressure plate  510  and plate  610 , respectively. In other embodiments, ramp surfaces can be angled at a greater or smaller angle. 
     Referring now to  FIGS. 9 and 10 , there is shown therein another exemplary continuously variable clutch wear compensation assembly  700 . The clutch compensation assembly  700  is continuously variable in that the assembly can adjust the axial position of pressure plate  710  in a manner directly proportional to the displacement caused by clutch wear. Clutch compensation assembly  700  also includes an electric motor  720 . The motor  720  is linked to a controller  730  (e.g., the transmission control unit as discussed with respect to  FIG. 1 ). Controller  730  and motor  720  act as the actuator  740  for the clutch compensation assembly  700 . Controller  730  is configured to control the adjustments of the compensation assembly according to distance to clutch engagement. The compensation assembly  700  includes a position sensor  750  placed with respect to a clutch assembly  760 . The compensation assembly  700  is configured to adjust pressure plate position according to a clutch actuation condition. 
     The clutch compensation assembly  700 , of  FIG. 9 , comprises a different cam interface than the previous embodiment. Cam interface  770  also enables the assembly to continuously adjust the position of pressure plate  710 . Cam interface  770  includes two matable, ramped surfaces having complementary angles—as also shown in FIG.  10 —that are radially angled with respect to the transmission. Surface  780  is coupled to plate  790 . On the opposite side of plate  790 , a pinion gear engages a worm gear linked to the servo motor (as shown in  FIG. 9 ). Bushings  800  are included in this embodiment to facilitate the rotation of the shaft  810  that extends between the motor  720  and worm gear  820 . Mating surface  830  is coupled to pressure plate  710 . As shown in  FIG. 8 , as plate  790  is vertically mobile with respect to the inner diameter of the transmission, pressure plate  710  is moved axially forward with respect to the transmission when plate  790  is moved toward the transmission center. Each ramped surface  780 ,  830  is angled approximately 20 degrees from the plate  790  and pressure plate  710 , respectively. In other embodiments, ramp surfaces are angled at a greater or smaller angle than shown. 
     While cam interfaces  580  and  770  are shown as two mating ramped surfaces, any number of cams can be incorporated in the clutch compensation assembly to enable continuous variation of clutch position. For example, in one embodiment, the pressure plate is configured with a pinion gear. A worm gear is coupled to an electric motor. The motor directly controls pressure plate position. Other cams including, for example, linkages and rotating cams can be married with the present teachings. 
     With reference to  FIG. 11 , the adjustment logic for the illustrated clutch compensation assemblies is shown. The graph  900  of  FIG. 11  compares stepwise adjustment logic with continuously variable adjustment logic. The distance to clutch engagement, caused by transmission wear is shown on the X-axis. Clutch adjustment is shown on the Y-axis. In a stepwise arrangement, the adjustment logic only adjusts clutch position once a certain displacement threshold is met. In this embodiment, the stepwise adjustment logic moves the pressure plate a predetermined distance (e.g., 0.10 mm) closer to a second pressure plate for every additional 0.10 mm of increased clutch engagement distance due to wear. This causes over- and under-compensation. The stepwise adjustment logic only accurately meets the necessary adjustment demands at several instances A, B and C. When the threshold is unmet, inefficiencies occur. With the continuously variable adjustment logic, adjustments are made on-demand or on an as-needed basis. The controller is linked to the position sensor so that the clutch compensation assembly can adjust with the distance to engagement caused by wear. The adjustment distance is proportional (and can be set to be equal to) the distance caused by component wear. 
     Referring now to  FIGS. 12-14 , there is disclosed a transmission controller or transmission control unit  1000  with software to execute some of the aforementioned techniques. The transmission control unit  1000 , as shown in  FIG. 12 , includes fan control logic  1010  and clutch wear compensation logic  1020 . Fan control logic  1010  is configured to govern the fan motor  1030  used to disperse air directly onto the face of the friction plates. Logic  1010  includes an inferred temperature model  1015  configured to infer clutch temperature based on inputs related to engine speed, clutch speed, engine torque and clutch torque. TCU  1000  is linked to two thermocouples  1040 ,  1050  positioned with respect to the transmission. Data from thermocouples  1040 ,  1050  can be process, as discussed below, in fan control logic  1010  to control fan operation. Clutch wear compensation logic  1020  is configured to control a clutch compensation motor  1060  to adjust a clutch pressure plate position according to a clutch actuation condition. The clutch actuation condition can be distance to clutch engagement or, for example, time to engagement. TCU  1000  is linked to a position sensor  1070  and timer  1080  to input data related to either clutch actuation condition as is discussed herein below. 
     In  FIG. 13 , the fan control logic  1010  of  FIG. 12  is shown in more detail.  FIG. 13  is an algorithm that controls operation of a fan motor. At step  1100  the software determines whether a difference between an inferred clutch temperature T infer  and an upper limit or threshold T upper  is greater than zero. If the inferred temperature is greater than the predetermined threshold fan speed is increased and the fan is turned on at step  1110 . Next the software tests to see if the difference between the inferred temperature and a lower threshold is less than zero at step  1120 . The lower threshold is the minimum temperature at which the fan is designated to operate. If the inferred temperature is less than T min , fan speed is decreased and the fan is turned off at step  1130 . If the inferred temperature is within the hysteresis range defined by the upper and lower thresholds the fan maintains its existing state of operation  1140 . The algorithm  1010  is a closed loop system; after step  1140  the software returns to step  1100  and the program is re-executed. 
     Thermocouple readings can be used to infer clutch temperature for the controller or send warning signals when transmission temperatures exceed a predetermined threshold. The temperature difference between thermocouples can be used to detect the heat generated by clutch assembly. Moreover, the temperature of the critical clutch surfaces is inferred. Input information supplied to the TCU includes engine speed, engine torque, input clutch speed and input clutch torque. Temperature is inferred from the relative speed between the engine and clutch or clutch slip. The power distribution or energy transfer rate is derived from clutch slip and used to infer temperature as disclosed in U.S. Patent Publication No. 2010/0113216 titled “Temperature Control of Dual Input Clutch Transmission.” Additional input information supplied to the TCU includes the specific heat of the clutches, the rate of heat convection from the clutches, and the weight and thermal conductivity of the clutches, the ambient temperature, coefficient of friction of the clutch surfaces, and initial temperature of the clutches. TCU is configured to process this data in order to calculate the rate of change of rotating power absorbed by the clutches. In another embodiment, measurements from the thermocouples are used to derive clutch temperature. The difference in temperature readings between two or more thermocouples (e.g.,  260  and  270  as shown in  FIG. 2 ) is used to calculate clutch heat dissipation. 
     Exemplary clutch wear compensation logic  1020 , as shown in  FIG. 14 , is configured to adjust a clutch pressure plate position according to a clutch actuation condition—distance to clutch engagement. The clutch wear compensation logic  1020  first detects if the clutch is engaged. A position sensor takes a reading of the clutch displacement necessary for engagement. The touch point (or distance to clutch engagement) is compared to a predetermined threshold at  1210 . If the distance to clutch engagement is greater than a predetermined threshold, the clutch compensation assembly is activated at  1220 . Clutch wear compensation is adjusted to lower the pressure plate touch point. The cam interface is adjusted to an offset that is less than or equal to the clutch engagement offset at  1220 . If the distance to clutch engagement is not above the predetermined threshold, the algorithm continues to step  1230 . If the touch point is too small, the algorithm continues to adjust the clutch wear compensation to raise the touch point at step  1240 . The algorithm  1020  is a closed loop system as well; after steps  1220  and  1240  the software returns to start and the program is re-executed. In this manner, if either adjustment steps  1220  or  1240  result in an excessive compensation, the system reverses the adjustment and corrects itself. 
     Other clutch actuation conditions can be programmed into the logic of  FIG. 14 . For example, audible detectors, torque sensors, and weight or inertia sensors data can be input into the TCU to govern the clutch compensation assembly. 
     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.