Patent Publication Number: US-2018038426-A1

Title: Expanding friction disk configurable to be compatible with wear liners and improved friction disks

Description:
PRIORITY/CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/748,033, filed Jun. 23, 2015, which claims priority to U.S. Provisional Application No. 62/015,978, filed Jun. 23, 2014 the disclosure of which is incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The presently disclosed technology relates to vehicle clutches, and more particularly to clutches with expanding friction disks. 
     BACKGROUND 
     This invention relates to a clutch system of the friction type placed in a power transmission system. Typical clutch systems include a clutch input such as a clutch basket, a clutch output such as a center clutch, and one or more plates making up a clutch pack and disposed between the clutch input and clutch output. When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled. The clutch pack is typically compressed by a pressure plate; the pressure plate typically providing a compressive force via a spring mechanism or through a centrifugally actuated mechanism. 
     Typically, such clutch systems include a clutch disengagement system consisting of a clutch lever mechanically coupled to the pressure plate such that when the clutch lever is actuated, the pressure plate&#39;s compressive force on the clutch pack is removed, disconnecting the rotational coupling between the clutch input and clutch output. Clutch disengagement systems typically couple the clutch lever to the pressure plate mechanically through a hydraulic actuation system or a cable actuation system. The clutch system incorporated in a 2011 Honda CRF-450R represents a typical prior art clutch system. 
     Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly. Typically, the multi-plate clutch is engaged/disengaged by the driver via a clutch lever mounted on the handlebar. Although the clutch lever operated clutch allows the driver to control the clutch engagement/disengagement, often times motorcycle drivers find the clutch lever difficult to operate smoothly. New riders have difficulty adjusting to smoothly engaging the clutch while operating the throttle to move the vehicle from a standing start. Experienced riders may need to partially disengage the clutch when traveling slowly to allow the engine to continue running without stalling. Motorcycle racers often have a difficult time controlling the engagement of the clutch and the application of the throttle to maximize acceleration. Off-road motorcycle racers often need to stop the rear wheel suddenly with the rear brake, causing the engine to stall if the clutch is not first disengaged. An automatic clutch can help overcome many of the problems associated with a manual clutch. 
     U.S. patent application Ser. No. 12/412,245 discloses an automatic clutch system incorporating an expanding friction disk and is incorporated herein by reference. 
     U.S. patent application Ser. No. 13/338,535 discloses a wear liner and improved friction disks and is incorporated herein by reference. 
     U.S. patent application Ser. No. 14/094,144 discloses an improved friction disk design and is incorporated herein by reference. 
     The prior art shows expanding friction disk designs comprised of centrifugal weights housed between a first plate and a second plate where the first plate and second plate are compressed together with biasing springs wherein the centrifugal weights, first plate and second plate contain features which provide a sliding contact interface between them with at least one side of the interface being a ramp mechanism. The ramp mechanism provides the relative lift to create expansion when the centrifugal weights move outwardly and overcome the biasing springs due to centrifugal force. In some designs the centrifugal weights are ball bearings which slide in grooves formed into either the first plate or second plate. 
     Although sliding contact between these parts and the respective ramp features provides good performance, there are application and design limitations associated with incorporating sliding contact between the centrifugal weights, first plate and second plate. These limitations include losses due to friction from the surface on surface sliding contact interfaces which can make optimizing the engagement and disengagement RPM difficult. In some cases the friction between the sliding contact areas is accentuated due to the presence of static and dynamic coefficient of friction differences inherent with sliding bearing interfaces. The friction loss and static to dynamic coefficient of friction transition can force the user to run an engagement point significantly higher than normal idle speed so that the disengagement point does not cause the engine to stall as the centrifugal weights return to their collapsed positions when engine RPM drops to idle. The engagement point is the RPM threshold where the centrifugal force of the centrifugal weights overcomes the biasing springs causing the expanding friction disk to expand causing the clutch pack and pressure plate to be pressurize resulting in the vehicle beginning to move. When the engagement point exceeds approximately 200 RPM above normal idle speed, the compression braking relied upon by many users is not adequate and a free-wheel affect can take place when the centrifugal weights return fully to their starting position and the clutch pack and pressure plate are no longer pressurized. 
     The static to dynamic coefficient of friction transition can also cause abrupt clutch engagement, which in certain terrain situations can make controlling power delivery from the engine to the drive train difficult resulting in a loss of traction at the driving wheel or wheels. This abruptness is preempted by the user having to rev the engine to a higher RPM than what the user would expect making it difficult to adapt to using the expanding friction disk while operating the vehicle. 
     The prior art shows the use of two vertically stacked ball bearings to provide rolling contact between adjacent parts. Although two vertically stacked ball bearings resolves the friction issues inherent with a sliding surface contact, the design is prone to wearing the mating features in the respective parts. Applied to an expanding friction disk, the parts prone to wear are the first plate and second plate which are in contact with the two vertically stacked ball bearings. When the first plate and second plate wear, the function of the expanding friction disk is degraded leading to clutch failure. 
     Therefore a need exists for an improved expanding friction disk assembly design which reduces friction specifically the difference between static and dynamic coefficient of friction at the base side and centrifugal weight interfaces and eliminates premature wear increasing the useful life of the expanding friction disk. 
     An expanding friction disk is significantly thicker than the standard friction disk it is intended to replace. Therefore, when using an expanding friction disk it is required to replace other clutch parts to accommodate the increased thickness of the expanding friction disk in order to maintain the same total number of friction surfaces as the original clutch included with the vehicle. The friction surfaces in a clutch correspond to the adjacent faces in contact between friction disks and drive plates which are interleaved within a clutch pack. Maintaining the same number of friction surfaces allows the compressive force transmitted through the pressure plate to remain the same and therefore maintains the same clutch lever pull force for the user while maintaining the same torque capacity within the clutch system. 
     Alternatively, an expanding friction disk can be used without replacing other clutch parts to accommodate the increased thickness of the expanding friction disk. In this situation additional friction disks and drive plates are removed to accommodate the increased thickness of the expanding friction disk while maintaining the same relative overall clutch pack height. Maintaining approximately the same overall clutch pack height is important in not disrupting the function of the clutch lever activated engagement/disengagement mechanism. With the additional friction disks and drive plates removed, the user is required to increase the compressive force transmitted through the pressure plate in order to maintain the same torque capacity as the original clutch included in the vehicle to counter-act the loss of friction surfaces. Increasing the compressive force transmitted through the pressure plate results in additional clutch lever pull force for the user which is undesirable as it makes the clutch lever more difficult to use when controlling the power delivery of the engine to the drive train. This clutch pack, with reduced surfaces, is also prone to overheating and slip which is undesirable. 
     Therefore a need exists for an expanding friction disk which is compatible with improved frictions disks of reduced thickness allowing the number of friction surfaces, clutch pack height and compressive force for the clutch system to be maintained. 
     It is therefore an object of the present invention to provide an improved expanding friction disk which operates with minimal friction and minimal difference between static and dynamic friction, has increased useful life by minimizing wear between centrifugal weights and the first plate and second plate, and which can be configured to operate with improved friction disks which utilize a wear liner to protect the clutch input. 
     SUMMARY OF THE DISCLOSURE 
     The purpose of the Abstract is to enable the public, and especially the scientists, engineers, and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection, the nature and essence of the technical disclosure of the application. The Abstract is neither intended to define the inventive concept(s) of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the inventive concept(s) in any way. 
     The disclosed technology is an expanding clutch disk. This clutch disk is designed to work in a clutch, such as those that are used in motorcycles. This type of clutch has a clutch basket with fingers and slots between the fingers, with the clutch basket typically made of aluminum in order to reduce weight. The clutch basket is loaded with friction disks that are either operatively attached to the clutch basket, or which are operably attached to the center clutch. The clutch basket is operatively attached to the motorcycle motor. The center clutch is operatively attached to the motorcycle transmission, and eventually to the wheel. The disclosed technology is an expanding disk which is placed among the friction disks in the clutch basket in order to change the thickness of the expanding disk based on RPMs. Under higher RPMs, certain curved pieces, called centrifugal actuating members, press towards the periphery of the expanding disk. The movement of these members pushes the first and second plate apart. This expansion is resisted by springs holding two disks together. The expansion is caused by cylindrical pins which force the plates apart as the centrifugal actuating members are pressed toward the periphery. 
     The disclosed expanding friction disk is made up of a generally planar and circular first plate and second plate. Both of these plates have inner and outer surfaces, with a number of centrifugal actuating members adjacent to the inner surface of each of the plates. At least one of these plates, such as the first plate, has at least one ramp, which is a blind slot defined in the inner surface of the first plate. The ramp has a ramped bottom surface, with the slot being deepest toward the center of the circular first plate, and less deep toward the periphery of the circular first plate. The slot is oriented transverse to a radial line from the center of the first circular plate. Corresponding to the slots in the plates, the centrifugal actuating members have pin sockets which surround and trap a cylindrical pin. Under higher RPMs, the centrifugal actuating members are pressed outward toward the periphery of the first plate, and the cylindrical pins in the centrifugal actuating members and in each of the blind slots moves up the ramp bottom in the ramp. As the cylindrical pin approaches the more shallow end of the ramp, the first plate is raised up from contact with the centrifugal actuating members, causing the expanding disk to be thicker. 
     Optionally, both the first plate and the second plate can each define a number of ramps on their inner surfaces, in which case the centrifugal actuating members would also have a pin socket and a cylindrical pin on each side of the centrifugal actuating members. 
     Optionally, the ramped bottom slots could be in the centrifugal actuating members, and the pin sockets could be in the first and or second plates. 
     The first and second plates are attached to each other by a number of springs, each spring biased to pull the plates together. The act of the springs pulling the plates together causes the expanding clutch disk to become thinner under lower RPMs or when stationary. 
     One or both of the first and second plates can also have a ball ramp for receiving or engaging a ball bearing which is also engaged in a ball socket on the centrifugal actuating members. There is a corresponding ball ramp on the first plate and or the second plate, with a bottom of the ball slot ramped, so as the centrifugal actuating members move outwardly, the ball in the ball ramp assists to raise the plates away from each other while keeping the centrifugal actuating members aligned correctly. The purpose of the balls is to further position in the centrifugal actuating members in the plates and also to assist in separating the first and second plate. The ball sockets on the centrifugal actuating members is a rounded bottom hole, which optionally passes through the centrifugal actuating member so that balls on each side of the centrifugal actuating member touch each other and contribute to each of them rolling together. One or both of the plates can have the balls and ball ramps. The position of the ball ramps and ball sockets can be reversed, with the plates having ball sockets, and the centrifugal actuating members having ball ramps. 
     Optionally, the ramps defined in the first plate and second plate may have rounded ends which further reduces friction and allows the pins to rotate more freely. 
     The disclosed technology also includes a clutch assembly having an expanding friction disk. The clutch basket of the assembly is generally cylindrical and has sidewalls and a closed first end and an open second end. The sidewalls of the clutch basket are made up of fingers which are arranged in a generally circular shape, with the fingers separated by slots between the fingers. The disclosed clutch assembly includes a number of U shaped wear liners which are placed in each slot, with the wear liners forming a tight fit with the sidewalls of the fingers and the base of the slot. The wear liners are formed of side pieces joined to a bottom piece. The wear liners are preferably made out of a hard material such as steel, and prevent the friction disk tabs of the friction disk from contacting the softer and lighter metal of the clutch basket. The side pieces of the wear liner have an attached capture flange, which engages the inside surface of each finger. 
     The disclosed clutch assembly includes a number of friction disks which are of three types. There are driving friction disks which have tabs which functionally connect to the clutch basket. There are driven friction disks which are not functionally connected to the clutch basket but which are functionally connected to the center clutch of the clutch. The third type of friction disk is an expandable disk, of which one or more is included in a stack of multiple friction disks which are housed within the clutch basket. A pressure plate is placed over the open end of the clutch basket and secured with bolts and springs to the center clutch. 
     Each driving friction disk is made up of a circular and planar disk with a hollow center portion. Each driving friction disk has a number of positioning tabs which extend out from the periphery of each driving friction disk and with the positioning tab engage with the wear liners which are placed in the slots of the clutch basket. 
     Interleaved among the driving friction disks are a number of driven friction disks. These do not have a positioning tab which extends outward into the slot area, but they have engagement tabs which extend toward the center of the clutch basket and which engage the center clutch. The driven friction disks are configured for frictional engagement with an adjacent driving friction disk. 
     The third type of friction disk in the disclosed clutch assembly is an expandable disk which is placed somewhere in the stack of friction disks inside the clutch basket. The expandable friction disk is of a type as described above, and has a first plate and a second plate, centrifugal actuating members, cylindrical pins, and optionally balls. This first plate and second plate are pressed together by spring tension, with the plates having a number of such springs holding them together. The centrifugal actuating members press outward under centrifugal force as the clutch basket spins, and the cylindrical pins provide rolling engagement and a force to press the first and second plate apart, when under sufficiently high centrifugal force. Under lower or no centrifugal force, then the centrifugal actuating members move toward the center point of the expanding friction disk, the cylindrical pins move into the deeper portion of the ramps, and the thickness of the expandable friction disk is decreased. 
     As noted in the description above, at least one of the first plate or the second plate has ramps with a sloping or ramped bottom. In one embodiment both the first plate and second plate have ramps with the ramped bottom. In that embodiment, the centrifugal actuating members have an elongated slot called a pin socket on each side to receive a cylindrical pin. In one possible embodiment of the invention, the centrifugal actuating members have ramps, and the first and second plates have pin sockets. 
     As noted in the description above, at least one of the first plate or the second plate has ramps with a sloping or ramped bottom. In one embodiment both the first plate and second plate have ramps with the ramped bottom. In that embodiment, the centrifugal actuating members have an elongated slot called a pin socket on each side to receive a cylindrical pin. The pin sockets on each side of the centrifugal actuating members being connected by a through slot allowing for the pins in each pin socket to contact and enable the pins to roll against each other. 
     The disclosed technology is also a method of modifying an existing motorcycle clutch with improved components for increased power, efficiency, heat dissipation and wear characteristics. The steps of this method start with disassembling an existing clutch. The clutch referred to is the type exemplified by a motorcycle clutch which has a clutch basket which is operationally attached to the motorcycle engine. The clutch basket is made up of fingers with slots between the fingers. The clutch basket has an enclosed first end, an open second end, a center clutch, a pressure plate, and friction plates that are placed inside the clutch basket. 
     The next step involves placing U shaped wear liners in the slots between the fingers in the clutch basket. The U shaped wear liners have two side pieces which are joined to a bottom piece, forming the U shape. There is a capture flange on each of the side pieces, which is configured to go inside the inside surface of the fingers of the clutch basket. The capture flanges keep the wear liners from flying out of the clutch basket when the clutch basket is spinning. 
     The next step is placing friction plates of three different types into the clutch basket. Some of these friction plates are driving, meaning that they have protruding tabs which fit between the fingers of the clutch basket. As the clutch basket turns, the driving friction plates also turn, and the edges of the protruding tabs engage the U shaped wear liners. This allows steel driving plates to be utilized, in a manner so that the edges of the steel protruding tabs do not wear on the inside edges of the fingers, which would typically be aluminum. The wear liners would typically be steel and would protect the inside of the fingers from wear from the projecting tabs. Interleaved with the driving friction plates are a number of driven friction plates. These connect with the driving friction plates by friction, and when pressure from the pressure plate is reduced, then the driven plates are disengaged from the driving plates. Driven plates have inward facing tabs which connect with a center clutch, with the center clutch being connected to a transmission and eventually to the wheel of a motorcycle. 
     The next step is placing a third type of friction plate in the stack of friction plates, and that is an expanding friction disk. This friction disk expands because of a result of centrifugal force, it is operatively connected to the clutch basket with protruding tabs that interface in the U shaped wear liners. 
     Each of the friction disks thus placed in the clutch basket are made up of a circular and planar disk which has a hollow center portion. The driving plates have a number of positioning tabs extending out from the periphery of each driving friction disk. 
     The friction disks which are mounted in the clutch basket are also made up of a circular and planar disk with a hollow center portion. The driven disks have a number of engagement tabs which extend toward the center of the disk engagement with ribs the center clutch, with the center clutch configured to rotate in relation to the clutch basket. The center clutch is operatively connected to the transmission and wheel, and the clutch basket is connected to the motor, and the two can be disengaged by a pressure plate, or engaged by pressure being placed on the friction plates to press them together. 
     The expandable disk is interleaved in the other friction disks and is configured to become thicker when it is subjected to centrifugal force, and it becomes thinner when the centrifugal force is reduced. The next step is attaching the pressure plate over the open second end of the clutch basket and securing with bolts and springs to the center clutch. 
     The expandable disk placed in the clutch basket is made up of a generally planar and circular first plate with an inner and outer surface, with the first plate inner surface defining at least one generally rectangular ramp. The ramp is a blind slot with a ramped floor, with the floor of the ramp being deepest toward the center of the first plate and less deep toward the periphery of the first plate. The slot is arranged transverse to a radial line from center to periphery of the first plate. 
     The expanding disk of this method has a number of centrifugal actuating members which are placed adjacent to the inner surface of the first plate. The actuating members have a first side and a second side and at least one of those sides defines a pin socket for receiving a cylindrical pin in each centrifugal actuating member. The cylindrical pin trapped in the pin socket in the centrifugal actuating members is free to rotate within that socket, and the cylindrical pin engages a ramp in the first plate. 
     The expanding disk using this method also includes a generally planar and circular second plate with an inner and outer surface with an inner surface facing the centrifugal actuating members. 
     In one embodiment of the device, both sides of the centrifugal actuating members have pin sockets and cylindrical pins, and the second plate as well as the first plate have ramps which engage the cylindrical pins. The first and second plates of the expanding disk used in this method are connected to each other by a number of springs pulling the plates together. Centrifugal actuating members are configured to move outwardly from the center of the disk by centrifugal force in a radial direction toward the periphery of the first and second plates. As the centrifugal actuating members move outwardly from the center of the first and second plates, the cylindrical pins roll up the ramp bottom of the ramps and press the two plates apart. When centrifugal force decreases, the springs push the cylindrical pins down the ramp, and press the first and second plates more closely together. 
     In one embodiment of the device, both sides of the centrifugal actuating members have pin sockets and cylindrical pins, and the second plate as well as the first plate have ramps which engage the cylindrical pins. The pin sockets used in this method being connected by a through slot and thus allowing the cylindrical pins to contact. The first and second plates of the expanding disk used in this method are connected to each other by a number of springs pulling the plates together. Centrifugal actuating members are configured to move outwardly from the center of the disk by centrifugal force in a radial direction toward the periphery of the first and second plates. As the centrifugal actuating members move outwardly from the center of the first and second plates, the cylindrical pins roll up the ramp bottom of the ramps and press the two plates apart. When centrifugal force decreases, the springs push the cylindrical pins down the ramp, and press the first and second plates more closely together. 
     The present invention for the improved expanding friction disk is disclosed in  FIGS. 1 through 12 . 
     Still other features and advantages of the presently disclosed and claimed inventive concept(s) will become readily apparent to those skilled in this art from the following detailed description describing preferred embodiments of the inventive concept(s), simply by way of illustration of the best mode contemplated by carrying out the inventive concept(s). As will be realized, the inventive concept(s) is capable of modification in various obvious respects all without departing from the inventive concept(s). Accordingly, the drawings and description of the preferred embodiments are to be regarded as illustrative in nature, and not as restrictive in nature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a preferred embodiment of an improved expanding friction disk; 
         FIG. 2A  is a top view of a preferred embodiment of an improved centrifugal weight also referred hereto as a centrifugal wedge; 
         FIG. 2B  is an isometric section view of a preferred embodiment of an improved centrifugal weight; 
         FIGS. 3A, 3B and 4  are section views of a preferred embodiment of an improved expanding friction disk; 
         FIG. 5  is an exploded view of a prior art clutch system; 
         FIG. 6  is a cross-section view of a prior art clutch system; 
         FIG. 7  is an isometric view of a prior art friction disk; 
         FIG. 8  is an exploded view of a preferred embodiment of an improved expanding friction disk configured within a clutch pack utilizing prior art friction disks; 
         FIG. 9  is a section view of a preferred embodiment of an improved expanding friction disk configured within a clutch pack utilizing prior art friction disks; 
         FIG. 10  is an exploded view of a preferred embodiment of an improved expanding friction disk configured within a clutch pack utilizing improved friction disks; 
         FIG. 11  is an isometric view of a preferred embodiment of an improved expanding friction disk, improved friction disk and wear liner; 
         FIG. 12  is a section view of a preferred embodiment of an improved expanding friction disk configured within a clutch pack utilizing improved friction disks. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While the presently disclosed inventive concept(s) is susceptible of various modifications and alternative constructions, certain illustrated embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the inventive concept(s) to the specific form disclosed, but, on the contrary, the presently disclosed and claimed inventive concept(s) is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the inventive concept(s) as defined in the claims. 
     Expanding friction disk centrifugal clutch systems are well known in the art and are typified by some of the products produced by Rekluse Motor Sports and include the Core EXP Clutch and EXP Clutch product lines for motorcycles and ATV&#39;s produced by Honda, KTM, Yamaha, Kawasaki and Suzuki among others. 
     An expanding friction disk is most commonly used with a typical clutch system comprised of a clutch input such as a clutch basket, a clutch output such as a center clutch, a pressure plate and one or more disks making up a clutch pack and disposed between the clutch input and clutch output. When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled. Such clutch systems typically include a clutch disengagement system consisting of a clutch lever mechanically coupled to the pressure plate such that when the clutch lever is actuated, the pressure plate&#39;s compressive force on the clutch pack is removed, disconnecting the rotational coupling between the clutch input and clutch output. Clutch disengagement systems typically couple the clutch lever to the pressure plate mechanically through a hydraulic actuation system or a cable actuation system. 
     An expanding friction disk is configured within the clutch pack like a typical friction disk and contains features coupling it rotationally to the clutch input when the clutch pack is under pressure. The pressure plate typically provides a compressive force via a spring mechanism and is typically biased away from the clutch pack so a gap exists when the expanding friction disk is not expanded. The clutch input is rotated by a motor and changes speed relative to motor speed changes, resulting in the expanding friction disk rotating with the clutch input. Centrifugal weights within the expanding friction disk are actionable causing the expanding friction disk to expand and thus remove the gap between the pressure plate and clutch pack resulting in the clutch pack becoming compressed and pressurized between the center clutch and pressure plate coupling the clutch input and clutch output. 
     Expanding friction disks are typically comprised by a plurality of centrifugal weights, a first plate, second plate and biasing springs where the biasing springs act on the centrifugal weights either directly or indirectly through features in the first plate and second plate. The centrifugal weights, first plate and second plate contain features and/or components providing at least one contact interface between each centrifugal weight and the first plate and second plate, where the contact interface is either a point, line, surface or rolling contact and can include a combination of contact interface types. Typically, at least the first plate provides a ramped mechanism for its contact interface with the centrifugal weight causing the expanding friction disk to expand when the centrifugal weights move in an outward radial direction. When the expanding friction disk reaches the threshold RPM where the centrifugal weights are able to overcome the biasing springs, the centrifugal weights move in an outward direction under centrifugal force causing the expanding friction disk to expand. 
     Expanding friction disks are typically much thicker than the standard friction disk they replace within the clutch pack. For example, the clutch system incorporated in a 2011 Honda CRF-450R utilizes a clutch pack incorporating eight friction disks which are approximately 3-millmeters thick and seven drive plates which are approximately 1.6-mm thick resulting in a clutch pack with an overall thickness of approximately 35.2-millimeters. By configuring a clutch pack with improved friction disks which are approximately 1.8-mm thick, and drive plates that are approximately 1.6 mm thick, a clutch pack can be configured using an expanding friction disk, seven improved friction disks and seven drive plates in approximately the same 35.2-millimeter space thus maintaining the equivalent number of friction surfaces in the clutch pack while allowing the user to retain the same compressive force transmitted through the pressure plate resulting in no change to clutch lever effort or to the overall system torque capacity. 
     Alternatively, utilizing clutch disks of reduced thickness provides the option to significantly increase the torque capacity of the clutch when specialized parts are also used creating maximum room possible for increased clutch disks allowing the user to lower the compressive spring force transmitted through the pressure plate while maintaining approximately the same torque capacity as the original clutch included with the vehicle while reducing burden for the user to active the clutch lever to disengage/engage the clutch system. 
     The present invention provides for a novel, improved expanding friction disk which operates with minimal friction and minimal difference between static and dynamic coefficients of friction, provides increased useful life by minimizing wear between centrifugal weights and bases sides, and which can be optionally configured to operate with improved friction disks utilizing a wear liner to protect the clutch input. Multiple embodiments are disclosed. 
     As depicted in  FIG. 1  the expanding friction disk  100  is comprised of first plate  101 , second plate  121 , centrifugal wedges  102 , biasing springs  103 , fasteners  104 , pins  105  and balls  106  where the first plate  101  and second plate  121  are identical. The first plate  101  and second plate  121  contain spring pockets  107 , spring cups  108 , ramp  109 , ball ramp  110 , weight stops  111 , and external tabs  112 . The first plate  101  and second plate  121  include friction pads  113  affixed to one side. The centrifugal wedges  102  contain pin sockets  115  and ball sockets  116 . In an alternative embodiment, the first plate  101  and second plate  121  are not identical where only the first plate  101  or second plate  121  contain the ramp  109  and ball ramp  110 . In yet another embodiment the first plate  101  and second plate  121  are not identical where the first plate  101  contains spring pockets  107  and the second plate  121  contains spring cups  108  while still allowing for the first plate  101  and second plate  102  to couple together. 
       FIG. 2A  discloses a top view of the centrifugal wedge  102 . Contained within the centrifugal wedge  102  are pin socket  115 , through slot  203 , pin slot web  201 , ball socket  116 , through hole  204  and ball socket web  202 . Stop notch  205  is also shown and corresponds to weight stop  111 . The centrifugal wedges  102  are shaped substantially like a segment of a typical friction disk profile in order to maximize the volume and therefore the mass and centrifugal effect of the centrifugal wedge  102 . In another embodiment the pin socket  115  contains features which support either end of a pin  105  in order to minimize side to side movement of the pin  105  and prevent wear between the ends of the pin  105  and corresponding ends of the pin socket  115 . 
       FIG. 2B  provides an isometric sectioned view of the centrifugal wedge  102 . In this view, the relationship between the pin sockets  115  on either side of the centrifugal wedge  102  and pin slot web  201  can be seen. Similarly, the relationship between the ball sockets  116  in each side of the centrifugal wedge  102  and ball socket web  202  can be seen. The centrifugal wedge  102  is symmetric about a first plane which is coincident to center line  207  and parallel to section-face  206 . The centrifugal wedge  102  is also symmetric about a second plane which is coincident to center line  207  and perpendicular to section-face  206 . 
       FIG. 3A  provides a section view of the expanding friction disk  100  sectioned through the center of two centrifugal wedges  102  one-hundred eighty degrees apart bisecting the pins  105  and balls  106 . The expanding friction disk  100  is in the collapsed state where the centrifugal wedges are at their respective inner most positions. The pins  105  are shown stacked in sets of two with one set of stacked pins  105  nested within each centrifugal wedge  102  via the opposing pin sockets  115  with the through slot  203  allowing the pins  105  to contact one another. Similarly, the balls  106  are configured in sets of two stacked adjacently with one set of stacked balls  106  contained within each centrifugal wedge  102  via the opposing ball sockets  116  with the through hole  204  allowing the balls  106  to contact one another. Each pin  105  operates against the ramp  109 . The ramp  109  being shown as a feature formed into the first plate  101 . The ramp  109  contains a back stop  301  to establish the inner position with respect to the axis  307  of the centrifugal wedge  102 . The back stop  301  also prevents the centrifugal wedge  102  with pins  105  and balls  106  from dislodging from the expanding friction disk  100  in the inward direction towards the axis  307 . Each ball  106  operates against a ball ramp  110 . The ball ramp  110  being shown as a feature formed into the first plate  101  and second plate  121 . The ball ramp  110  includes a ball ramp back stop  302  which serves similar purposes as the back stop  301 . Pin slot web  201  is positioned between the opposing pin sockets  115  formed on both sides of the centrifugal wedge  102 . Ball socket web  202  is positioned between the opposing ball sockets  116  formed on both sides of the centrifugal wedge  102 . Pin slot web  201  and ball socket web  202  limit the amount of free movement of the centrifugal wedge  102  in the upward direction  305  and downward direction  306  preventing the centrifugal wedge  102  from rocking excessively and interfering with the first plate  101  and second plate  121  as the centrifugal wedge  102  travels outward from center axis  307 . When the centrifugal wedges  102  travel outward from center axis  307  the distance the centrifugal wedges  102  can travel is limited by the weight stops  111  of the first plate  101  and second plate  121  because the stop notches  205  will contact the inner wall of the weight stops  111 . When the centrifugal wedges  102  travel outward from center axis  307  the first plate  101  and second plate  121  are displaced away from one another as the pins  105  and balls  106  roll along the ramp  109  and ball ramp  110  respectively. In one embodiment the expansion of the expanding friction disk  100  is limited to approximately 0.050-inch. In another embodiment the expansion of the expanding friction disk  100  is limited to 0.080-inch. In yet another embodiment the stacked pairs of pins  105  do not physically contact one another, but rather are in contact with at least one set of two stacked ball bearings which maintains the rolling contact between the pins  105  and respective ramps  109 . In yet another embodiment, pin-like features are formed onto the centrifugal wedge  102  providing contact with the ramps  109  similar to the pins  105  where the pin-like features are coated with a friction reducing material providing sliding contact between the pin-like features and respective ramps  109  and where the friction reducing material provides minimal difference between static and dynamic coefficient of friction thus closely matching the performance associated with rolling contact. In yet another embodiment the balls  106  are replaced with rolling elements or pins similar to the pins  105  but of a shorter length. 
       FIG. 3B  provides a section view of the expanding friction disk  100  sectioned through the center of one of the centrifugal wedges  102 . The centrifugal wedge  102  is shown in its outer most position after centrifugal force as moved the centrifugal wedges  102  out resulting in the expansion of the expanding friction disk  100 . 
       FIG. 4  is a section view of the expanding friction disk  100  sectioned through the center of two fasteners  104  one-hundred eighty degrees apart. The alignment between first plate  101  and second plate  121  is shown where the spring cup  108  indexes into the spring pocket  107 . In another embodiment the first plate  101  and second plate  121  do not contain both spring cups and spring pockets and only contain spring cups or spring pockets. The flange  402  of the spring cup  108  supports the biasing spring  103  on one end, while the fastener flange  403  retains the other end of the biasing spring  103 . The fastener  104  attaches into the fastener boss  401  shown in the floor of the spring pocket  107  of the first plate  101 . In one embodiment the fastener  104  contains features that interlock into corresponding recessed pockets contained by the fastener boss  401  after the fastener is passed through the fastener boss  401  and rotated approximately ninety degrees. In another embodiment the fastener  104  threads into the fastener boss  401 . In yet another embodiment the fastener  104  is held in relation to the fastener boss  401  via a retaining ring. When the centrifugal wedges travel in an outward direction away from center axis  307  the first plate  101  and second plate  121  move further apart in relation to one another compressing the engagement spring further. 
     From  FIG. 3A, 3B  and  FIG. 4  the function of the expanding friction disk  100  is disclosed. The biasing springs  103 , through the flange  402  and fastener  104 , compel the first plate  101  and second plate  121  together securing the centrifugal wedges  102  with pins  105  and balls  106  within the ramp  109  and ball ramp  110  respectively. As the expanding friction disk is rotated about the center axis  307  centrifugal forces urge the centrifugal wedges  102  in an outward direction away from the center axis  307 . When sufficient rotational speed is achieved, the centrifugal force of the centrifugal wedges  102  exceeds the force of the biasing springs  103  and compels the paired sets of pins  105  and paired sets of balls  106 , contained within each centrifugal wedges  102 , to roll in in contact with the ramp  109  and ball ramp  110  respectively in an outwardly direction away from the center axis  307 . As the centrifugal wedges  102  with respective pins  105  and balls  106  advance away from the center axis  307  the first plate  101  and second plate  121  are displaced away from one another along a path parallel to the center axis  307  resulting in the expanding friction disk  100  expanding. 
     When the centrifugal wedges  102  travel outward from center axis  307  the distance the centrifugal wedges  102  can travel is limited by the weight stops  111  of the first plate  101  and second plate  121  when the stop notches  205  contact the inner wall of the weight stops  111 . 
       FIG. 5  is an exploded view of a prior art clutch. The configuration of the clutch basket  508 , center clutch thrust washer  507 , center clutch  506 , center clutch nut  505 , throw-out  504 , friction disk  516 , drive plate  515 , pressure plate  503 , standard springs  502  and spring bolts  501  are typical of most modern motorcycle clutches, this structure is commonly employed in many types of power transmission devices. Clutch pack  520  is comprised of friction disks  516  and drive plates  515 . The clutch basket  508  contains slots  509  which receive the friction disk tabs  517  and thus coupling the clutch basket  508  and friction disks  516  rotationally. The center clutch  506  contains a profiled ring  510  which provides rotational coupling to the teeth  518  of the drive plates  515 . The clutch basket  508  is typically coupled rotationally to a power input source such as an engine and the center clutch  506  is typically coupled rotationally to an output such as a transmission. In another embodiment the clutch basket  508  is coupled rotationally to an output and the center clutch  506  is coupled rotationally to a power input. Typically the clutch basket  508  contains an opening in the center for receiving a transmission input shaft (not shown); the clutch basket  508  is configured with a bearing between the clutch basket  508  and the transmission input shaft so that the clutch basket  508  can rotate independently of the transmission input shaft with minimal friction. Typically a center clutch thrust washer  507  is disposed between a center clutch  506  and the clutch basket  508 . A center clutch nut  505  secures the center clutch  506  against the center clutch thrust washer  507  which in turn is secured against a shoulder (not shown) on the transmission input shaft. The center clutch is typically rotationally coupled to the transmission input shaft via a suitable spline. 
       FIG. 6  is a section view of the prior art clutch shown in  FIG. 5 . As best seen in  FIG. 6 , the clutch pack  520  is comprised of eight friction disks  516  and seven drive plates  515 . The clutch pack  520  establishes the distance between the pressure plate flange face  602  and center clutch flange face  605 . The standard springs  502  act on the pressure plate  503  to compress the clutch pack  520  forcing the adjacent surfaces of the friction disks  516  and drive plates  515  to become coupled rotationally and in turn coupling the basket  508  and center clutch  506  rotationally. The throw-out  504  is coupled to a clutch disengagement system (not shown). The clutch disengagement system (not shown) is operable to selectively position the throw-out  504  for the purpose of pushing the pressure plate  503  away from the clutch pack  520  to disengage the clutch. Alternatively, the clutch disengagement system (not shown) is operable to selectively position the throw-out  504  for the purpose of returning the pressure plate  503  into contact with the clutch pack  520  to engage the clutch. In another embodiment the clutch pack  520  is comprised of nine friction disks  516  and eight drive plates  515 . In the preferred embodiment the clutch pack  520  is comprised of eight 3-millimeter thick friction disks  516  and seven 1.6-millimeter drive plates  515  resulting in the clutch pack  520  being approximately 35.2-millimeters tall. In other prior art the clutch pack  520  is less than 35-millmeters tall and is comprised of eight friction disks and seven drive plates that are less than 1.6-millimeters thick. In yet other prior art, the clutch pack  520  is taller than 35.2 millimeters and is comprised of nine friction disks which are approximately 4-millimeters thick and eight drive plates which are approximately 2-millimeters thick. 
       FIG. 7  is an isometric view of a prior art friction disk  516  utilized in the prior art clutch.  FIG. 7  shows rectangular pads  718  affixed to the friction disk  516 . The rectangular pads  718  are affixed to both sides of the friction disk  516 . The rectangular pads  718  are typically a composite material where the material has frictional properties suited for engaging adjacent surfaces of drive plates  515  with which the friction disks  516  contact. In another embodiment, the friction disk  516  utilizes forty-eight rectangular pads  718  per side. In another embodiment twenty-four rectangular pads  718  per side are used. In yet another embodiment the rectangular pads  718  are wider and therefore approach a more square shape. 
       FIG. 8  is an exploded view of the prior art clutch shown in  FIG. 5  utilizing a revised clutch pack  820  which includes the expanding friction disk  100 , friction disks  516  and drive plates  515 . The basket contains slots  509  which receive the friction disk tabs  517  and external tabs  112  of the expanding friction disk  100 . The expanding friction disk  100  profile is designed to match that of a friction disk  516  thus providing similar rotational coupling to the basket  508 . In another embodiment where the center clutch  506  is coupled rotationally to a power input and the basket  508  is coupled rotationally to a power output the expanding friction disk  100  profile is designed to match that of a drive plate  515  in order to provide rotational coupling to the center clutch  506 . Stronger springs  802  are also shown and provide increased force as compared to the standard springs  502  used in the prior art clutch shown in  FIG. 5 . The stronger springs  802  are required to compensate for fewer friction surfaces within the revised clutch pack  820  as compared with the clutch pack  520  for the purpose of maintaining the overall torque capacity of the clutch system when clutch pack  820  is used in place of clutch pack  520 . 
       FIG. 9  is a section view of the prior art clutch utilizing the revised clutch pack  820  including the expanding friction disk  100  shown in  FIG. 8 . As best seen in  FIG. 9  the clutch pack  820  is comprised of five friction disks  516 , five drive plates  515  and the expanding friction disk  100 . A gap  901  exists between the pressure plate flange face  602  of the pressure plate  503  and friction face  604  of the friction disk  516 . Creating the gap  901  is typically done via an external adjuster acting on the clutch disengagement system and thus on the throw-out  504  to bias the pressure plate  503  in a direction away from the clutch pack  820 . Other methods for biasing the pressure plate  503  to create a gap  901  exist in the prior art and any method can be employed. When the centrifugal wedges  102  travel outward from center axis  307  they displace the first plate  101  and second plate  121  eliminating the gap  901  and thus engaging the pressure plate  503  and standard springs  502  pressurizing the clutch pack  520  and thus coupling the basket  508  and center clutch  506  and thus the clutch input to the clutch output. Maintaining approximately the same distance between the pressure plate flange face  602  and center clutch flange face  605  is important as to not disrupt the spacing and function for the clutch disengagement system (not shown) coupled to the throw-out  504 . Significantly changing the spacing between the pressure plate flange face  602  and center clutch flange face  605  can hinder the function of the clutch disengagement system (not shown) and/or the user&#39;s ability to operate the clutch disengagement system. 
       FIG. 10  is an exploded view of the prior art clutch shown in  FIG. 5 , utilizing an improved clutch pack  1020  comprised of an adapted expanding friction disk  1000 , improved friction disks  1016  and drive plates  515 . The basket  508  contains slots  509  which receive the wear liners  1005  therefore rotationally coupling the clutch pack  1020  to the basket  508  via the wear liners  1005 . Standard springs  502  are also shown being used with the improved clutch pack  1020 . The improved clutch pack  1020  allows the use of the standard springs  502  because the improved clutch pack  1020  retains the same number of friction surfaces as the clutch pack  520  and thus torque capacity of the clutch system is maintained. Furthermore, since the improved clutch pack  1020  allows the use of the standard springs  502 , the effort required to operate the clutch disengagement system is unchanged offering a significant advantage for the user compared to the clutch pack  820 . 
       FIG. 11  is an isometric view of an improved friction disk  1016 , a wear liner  1005  and adapted expanding friction disk  1000 . The modified first plate  1101  and modified second plate  1121  of the adapted expanding friction disk  1000  are designed to match the profile of the improved friction disk  1016 . The disk tabs  1117  of the improved friction disk  1016  and the modified external tabs  1112  of the modified first plate  1101  and modified second plate  1121  are sized appropriately to fit within the liner opening  1110  of the wear liners  1005 . The wear liner  1005  consists of a U-shaped profile with liner opening  1110  and ID capture flange  1111 . The ID capture flange  1111  prevents the wear liner  1005  from separating from the basket  508  due to centrifugal forces acting on the liner  1005  when the basket  508  is rotating. In an alternative embodiment, the modified first plate  1101  and modified second plate  1121  are not identical where only the modified first plate  1101 , or modified second plate  1121  contain the ramp  109  and ball ramp  110 . In yet another embodiment the modified first plate  1101  and modified second plate  1121  are not identical where the modified first plate  1101  contains spring pockets  107  and the modified second plate  1121  contains spring cups  108  while still allowing for the modified first plate  1101  and modified second plate  1121  to couple together. 
     In  FIG. 11  the adapted expanding friction disk  1000  is shown configured with the centrifugal wedges  102 , fasteners  104  and friction pads  113  showing that the adapted expanding friction disk  1000  is comprised of the same components as the expanding friction disk  100  with the exception of the modified first plate  1101  and modified second plate  1121  which are adapted to function with the wear liner  1005  such that the modified external tabs  1112  are appropriately sized to fit within the liner opening  1110 . 
     Also shown in  FIG. 11 , the improved friction disk  1016  is comprised of disk tabs  1117  and friction segments  1118  where the disk tabs  1117  are appropriately sized to fit within the liner opening  1110 . Furthermore, the friction segments  1118  are designed to minimize parasitic drag when pressure is removed from the improved clutch pack  1020 . Parasitic drag exists whenever the surfaces in contact between improved friction disks  1016  and drive plates  515  decouple but remain in close proximity to one another allowing surface tension in cooling fluid such as oil to cause parasitic drag and/or incidental contact to cause parasitic drag. The design of the friction segments  1118  and their respective arrangement on both sides of the improved friction disk  1016  allow the improved friction disks  1016  to rotate independently of the drive plates  515  with an acceptable amount of parasitic drag. Optimizing the shape and features of the friction segments  1118  with respect to reducing parasitic clutch drag is important in allowing the improved friction disks  1016  to decouple from the drive plates  515  when the adapted expanding friction disk  1000  is collapsed and providing the gap  901 . In other embodiments where more than seven improved friction disks  1016  are configured with interleaved drive plates  515 , the friction segment  1118  design maintains approximately the same amount of parasitic drag as the clutch pack  1020 . In these embodiments the advantage of configuring the clutch to accommodate more than seven improved friction disks  1016  further enhances performance aspects of the clutch. One option made possible if more than seven improved friction disks  1016  are used is for the user to utilize lighter springs providing less force than the standard springs  502  in order to reduce effort in operating the clutch disengagement system (not shown), but while maintaining similar torque capacity to typical clutch pack utilizing eight friction disks  516 . 
       FIG. 12  is a section view of the prior art clutch utilizing the adapted expanding friction disk  1000  and improved clutch pack  1020  shown in  FIG. 10 . As best seen in  FIG. 12  the clutch pack  1020  is comprised of seven improved friction disks  1016 , seven drive plates  515  and the adapted expanding friction disk  1000 . The gap  901  exists between the pressure plate flange face  602  of the pressure plate  503  and the top face  1204  of the modified expanding friction disk  1000 . The improved clutch pack  1020  along with gap  901  maintain approximately the same distance between the pressure plate flange face  602  and center clutch flange face  605  in order to not disrupt the spacing and function of the clutch disengagement system (not shown) coupled to the throw-out  504 . Significantly changing the spacing between the pressure plate flange face  602  and center clutch flange face  605  can hinder the function of the clutch disengagement system (not shown) and/or the user&#39;s ability to operate the clutch disengagement system. The improved clutch pack  1020  provides the equivalent number of surfaces as the clutch pack  520  and therefore maintains the same torque capacity using the standard springs  502 . Providing an improved clutch pack  1020  with the adapted expanding friction disk  1000  provides many performance advantages including, lower operating temperatures, use of the standard clutch springs which provide no change in effort for operating the clutch disengagement system (not shown). In an alternative embodiment the clutch pack  1020  is configured with the adapted expanding friction disk  1000  located in the middle of the clutch pack  1020 . In yet another embodiment the clutch pack  1020  is configured with the adapted expanding friction disk  1000  located at the bottom, or near the bottom of the clutch pack  1020 . 
     While certain preferred embodiments are shown in the figures and described in this disclosure, it is to be distinctly understood that the presently disclosed inventive concept(s) is not limited thereto but may be variously embodied to practice within the scope of the following claims. From the foregoing description, it will be apparent that various changes may be made without departing from the spirit and scope of the disclosure as defined by the following claims.