Abstract:
An improved liner and friction disk for a clutch basket is disclosed. The improved liner is easily retrofitted into a typical clutch basket and is held in place without fasteners or adhesives or special changes to the clutch basket. The improved liner is held in place without consideration to the outer diameter of the basket allowing the liner to work with a wider range of clutch basket designs and sizes. The liner provides an improved wear surface for the clutch basket&#39;s engagement surface with the driving friction surface. A friction disk with tabs adapted to fit inside the narrowed space provided by the improved liner is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    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. Most clutch systems can be disengaged by means of a lever acting on a clutch throwout which pushes the pressure plate away from clutch pack, rotationally decoupling the clutch input and clutch output. 
         [0002]    Most motorcycles incorporate a clutch system whose clutch pack includes multiple driving friction plates and driven plates. The driving friction plates are typically formed from aluminum with friction material bonded to both sides of the plate. The driving friction plates are typically coupled rotationally with the clutch basket. Driven plates are typically formed from steel and are typically coupled rotationally with the center clutch. 
         [0003]    Most motorcycles incorporate a clutch basket that is formed from aluminum. Aluminum is inexpensive to cast and lightweight relative to other materials such as steel. However, one disadvantage of aluminum for constructing a clutch basket is that it is soft relative to other materials such as steel. Significant wear at the surfaces on the clutch basket where the driving friction disks engage the clutch basket is a common problem. 
         [0004]    One problem with forming the driving friction plates from aluminum is heat storage and heat expansion. When the clutch slips, during take-off for example, heat is generated. The driving friction plates and driven plates absorb this heat until the heat can dissipate out of the clutch system. If the clutch slips excessively, the heat build-up can be significant; causing the clutch pack to expand. When the clutch pack expands from heat, the pressure plate is pushed away from the clutch throwout; requiring more lever movement to rotationally decouple the clutch input and clutch output. This phenomenon is known as “clutch fade”. 
         [0005]    It is well known that steel, by volume, has more thermal capacity and a lower thermal coefficient of expansion than aluminum. By forming the friction plate from steel instead of aluminum, given the same amount of slip and therefore the same amount of heat generation, a clutch system incorporating driving friction disks formed from steel will have reduced “clutch fade” vs. a clutch system incorporating driving friction disks formed from aluminum. 
         [0006]    However, steel is typically much harder than aluminum. When a driving friction disk formed from steel is used in place of a driving friction disk formed from aluminum, wear at the surfaces on the aluminum clutch basket where the driving friction disks engage the clutch basket is accelerated. 
         [0007]    The KTM 2006 450 SXF motorcycle model uses driving friction plates formed from steel and a clutch basket formed from steel. The KTM motorcycles are considered a premium brand and are generally more expensive than similar motorcycles from other manufactures. Most modern motorcycles use driving friction plates and a clutch basket formed from aluminum. 
         [0008]    One way to overcome the problem of excessive wear of the clutch basket from the driving friction plates is to form the clutch basket from a harder, more wear resistant material such as steel. However, forming a clutch basket from steel would increase its weight and likely its cost versus a clutch basket formed from aluminum. A lightweight clutch basket is advantageous in that it has less reciprocating mass; allowing for quicker acceleration than a heavier clutch basket. 
         [0009]    Typically the driving friction plates wear out and are replaced several times before the clutch basket is replaced due to wear. Requiring the owner of a vehicle to purchase a new clutch basket to prevent rapid wear from the use of improved driving frictions plates formed from steel is undesirable for both cost and increased weight of the clutch basket. 
         [0010]    Steel is also stronger than aluminum. Forming the driving friction plate from steel allows the use of a driving friction plate that is thinner than a comparable aluminum driving friction disk and having the same strength. It is well known that by using more driving friction plates in a clutch system that the clutch system will have greater torque capacity assuming equal spring pressure. However, a thinner driving friction plate will have even greater wear characteristics against a relatively soft clutch basket due to the reduced surface area at the point of engagement with the clutch basket. 
         [0011]    Taylor in U.S. Pat. No. 7,287,632 and Martin in U.S. Pat. No. 6,708,807 have proposed using liners, formed from a hard material such as steel, between the clutch basket and the driving friction plates to reduce wear and provide a replaceable wear surface. Both U.S. Pat. No. 7,287,632 and U.S. Pat. No. 6,708,807 are included herein by reference. Such a liner could be very advantageous in use, especially when combined with driving friction plates formed from steel. However neither Taylor nor Martin have proposed a liner that could easily be adapted by the owner of the vehicle to most common existing clutch baskets. Martin proposes a liner that slides into place without fasteners or adhesives but requires a clutch basket that was designed to accept the liner. Most common existing clutch baskets were not designed to accept a liner such as proposed by Martin. The liner disclosed by Martin requires a clutch basket with substantially recessed planar inner edges and recessed planar outer edges including a well-defined distance between the edges to capture U-shaped retaining clips on each leg. Most modern motorcycle clutch baskets are formed with an inner diameter and an outer diameter. Furthermore, the distance between the inner and outer diameter of the clutch basket varies greatly between clutch basket models. A liner solution that requires retention on the outer and inner diameter will not work on a wide variety of clutch baskets. 
         [0012]    Taylor proposes a liner that could be adapted to most common existing clutch baskets but requires some form of adhesive or fastener to hold the liner in place. Securing the liners proposed by Taylor with an adhesive or a fastener is not something that most vehicle owners will be easily capable of doing. Typically, this operation would need to be performed by a specialized repair or remanufacturing facility or be manufactured as part of the original clutch basket. Furthermore, at least some of the liners disclosed by Taylor adapt to and engage both the inner and outer diameter of the clutch basket. Typically many different vehicles from many different manufactures will use a friction disk of the same dimensions. This requires the interior features of the clutch basket to be very similar between many different manufacturers. However, the exterior features of the basket tend to be different between different manufactures because the driving friction disks do not locate on the exterior features. Furthermore, there is often very limited space between the outer diameter of the clutch basket and the engine case; in many cases, a liner covering the outer diameter of the clutch basket could interfere with the engine case. 
         [0013]    Therefore, a need exists for an improved liner for a vehicle&#39;s existing clutch basket that can easily be installed by the vehicle owner, without special tools or adhesives. A need exists for the liner to be restrained from radial outward movement by the inner diameter of the clutch basket so as to work with the stock clutch basket supplied with most modern motorcycles. The improved liner should provide improved wear resistance to the clutch basket driving friction plate engagement surfaces; especially when used in conjunction with a driving friction plate formed from steel or other material that has increased wear properties against the vehicle clutch basket. Furthermore, a need exists for a clutch pack system with improved resistance to heat induced “clutch fade”, that will easily retrofit into a vehicle&#39;s existing clutch system without imposing increased wear on the clutch basket&#39;s driving friction plate engagement surfaces. The improved clutch pack&#39;s friction disk should incorporate a clutch basket engagement tab with reduced width versus the standard friction disk so as to fit in the narrowed space provided by the improved liner. 
         [0014]    Heretofore, no one has proposed a liner system than can easily be adaptable by a typical vehicle owner to an existing typical vehicle standard clutch basket, without fasteners or adhesives. Furthermore, no one has proposed a friction disk system whose driving friction plates are formed from a material that offers improved thermal heat capacity vs. the original driving friction plates and that can be retrofitted into an existing clutch basket that is formed from a material softer than the improved friction disk material, without creating accelerated wear on the clutch basket&#39;s driving friction plate engagement surfaces and that includes a clutch basket engagement tab with a reduced width to fit within the narrowed slot space provided by the improved liner. 
         [0015]    Therefore, it is one object of the invention to provide a friction disk system with improved thermal properties and less thickness than a standard aluminum friction disk that can operate within a standard clutch basket without accelerating the wear of the standard clutch basket in operation. It is another object of the invention to provide a liner system that can easily be retrofitted to a clutch basket that was not designed to use a liner system, without the need for special tools or fasteners. It is another object of the invention to provide the improved liner system in conjunction with a friction disk system with improved thermal properties and less thickness and formed with clutch basket engagement tabs whose width is selected to fit inside the narrowed space provided by the improved liner system. 
         [0016]    A preferred embodiment of the present invention is shown in  FIGS. 1 through 5 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is an exploded view of a prior art typical clutch system; 
           [0018]      FIG. 2  is a view of a single prior art typical driving friction disk in engagement with a typical clutch basket; 
           [0019]      FIGS. 3   a  and  3   b  show views of the improved liner; 
           [0020]      FIG. 4  is a view of the improved liner installed into a typical prior art clutch basket; 
           [0021]      FIG. 5  is a view of the improved liner installed into a typical prior art clutch basket and in engagement with the improved driving friction disk; 
           [0022]      FIG. 6  shows a top detail view of the improved friction disk clutch basket engagement tab, engaged with the improved liner and installed into a typical prior art clutch basket. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Reference throughout this specification to “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
         [0024]    Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
         [0025]    The present invention provides for a novel wear resistant liner for a clutch basket. The improved liner is particularly useful when used with driving friction plates formed from a material harder than the clutch basket to reduce wear on the clutch basket. 
         [0026]      FIG. 1  shows the major components of a typical prior art multi-plate clutch system as used in a modern motorcycle. The clutch system of  FIG. 1  is also representative of multi-plate clutch systems used in other types of vehicles and machinery. 
         [0027]    Referring again to  FIG. 1 , the clutch basket  110  is typically rotationally connected to a power source (not shown). A center clutch  108  is typically rotationally coupled to an output such as a transmission shaft (not shown). The center clutch nut  106  and washer  107  secure the center clutch to the transmission shaft. The thrust washer  109  allows the clutch basket  110  to spin independently of the center clutch  108 . A clutch pack  105  includes driving friction plates interleaved with driven plates. The driving friction plates are coupled rotationally to the clutch basket  110  and driven plates rotationally coupled to the center clutch  108  such that when no pressure is applied to the clutch pack  105 , the driving friction plates are able to turn relative to the driven plates and when pressure is applied to the clutch pack  105 , a rotational torque can be transmitted from the clutch basket  110  to the center clutch  108 . Pressure plate bolts  101  secure a pressure plate  103  to the center clutch  108  through pressure plate springs  102  such that the pressure plate spring  102  force is transmitted to the clutch pack  105 . A throwout  104  is provided, typically coupled to a lever through an actuator rod (not shown) to lift the pressure plate  103  away from the clutch pack  105 , releasing the spring force against the clutch pack  105 . 
         [0028]      FIG. 2  shows the prior art clutch basket  110  in engagement with a single prior art driving friction plate  201 . The driving friction plate  201  includes a plurality of driving friction plate tabs  203  and a plurality of friction pads  202 . The clutch basket  110  includes a plurality of fingers  210 . Between each finger  210  is a slot  212  to engage a driving friction plate tab  203 . The edge of each finger  210  has a clutch basket driving engagement surface  211  to engage and rotationally couple the driving friction plate  201 . The clutch basket is subject to wear from the driving forces applied to the driving friction plate tab  203 . The rate of wear will generally be increased when the driving friction plate tab  203  is made from a material harder than the clutch basket. 
         [0029]      FIGS. 3   a  and  3   b  show one embodiment of the improved clutch basket liner  301 . The clutch basket liner is generally U-shaped, with two legs  302  connected by a base  305 . The legs  302  are at an angle of approximately 90 degrees to the liner base. In another embodiment, the legs  302  are at angle greater than 90 degrees to the liner base. In this embodiment, the increased angle will require the legs to apply an outward spring force against the clutch basket, helping to hold the liner  301  in place during installation. 
         [0030]    Extending from each leg  302  at a slightly obtuse angle is an ID capture flange  303 . At an end of each driving friction plate leg  302  is an optional hole  304 . The hole  304 , when used with a suitable tool, can be used to lift the liner and entire clutch pack out of the clutch assembly. The liner base  305  captures the nearest driving friction plate tab  203  and lifts the entire clutch pack  105  with the liner  301 , out of the clutch basket  110 . 
         [0031]      FIG. 4  depicts the improved clutch basket liner  301  installed between adjacent fingers  210  of the prior art clutch basket  110 . The two legs  302  cover the surface of the clutch basket driving engagement surface  211  (not visible in  FIG. 4 ). The clutch basket liner  301  is restrained from radial outward movement by the ID capture flange  303  engaging the inner surface  401  of the clutch basket. The obtuse angle allows the ID capture flange  303  to conform closely to the inner diameter of the basket and provides clearance to the friction disk outer diatmer. The optimal angle between the ID capture flange  303  and the legs  302  is determined by the inner diameter of the basket: a smaller basket inner diameter requires a larger angle and a larger basket inner diameter requires a smaller angle. In one embodiment, the optimal angle between the ID capture flange  303  and the legs  302  is 95 degrees. The capture flange  303  prevents the clutch basket liner  301  from being flung radially out of the basket due to centrifugal force when the clutch basket  110  rotates. 
         [0032]      FIG. 5  depicts the improved clutch basket liner  301  installed into the prior art clutch basket  110  with a clutch pack  105  having driving friction disks  501  formed with narrowed driving friction plate tabs  502  to fit within the narrowed slot provided by the clutch basket liner  301 . In this view, it can be seen that the clutch basket liner  301  is retained from axial movement out of the clutch basket  110  by the friction plate tabs  503  directly adjacent to the liner base  305 . 
         [0033]      FIG. 6  shows a top view of the improved clutch basket liner  301  installed between the clutch basket fingers  210 , the driving friction plate tab  502  disposed between the legs  302  and the ID capture flanges  303  disposed between the inner diameter locating surface  401  of the clutch basket  110  and the major diameter  601  of the driving friction disk  501 . In this view it can be seen that the clutch basket liner  301  would be restrained from inward movement by the ID capture flanges  303  coming into contact with the major diameter  601  of the driving friction disk  501 . 
         [0034]    The 2009 Honda CRF-450R uses a typical standard clutch basket. The width of the slot  212  formed between the fingers  210  is approximately 0.550″. The standard driving friction plate tabs  203  are 0.540″ wide leaving a clearance of 0.010″. In one embodiment, the improved clutch basket liner  301  is formed from material have uniform thickness of 0.030″. With the improved clutch basket liner  301  installed, the width of the slot with the liner installed is 0.490″, the narrowed driving friction plate tabs  502  are 0.480″ wide also leaving a clearance of 0.010″. 
         [0035]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.