Abstract:
A novel clutch separator plate is disclosed. The improved clutch separator plate incorporates openings which pass over the friction pads of a friction plate to improved thermal stability, reduce drag and provide consistent and positive engagement.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to provisional application 61/738,512. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to a clutch system of the friction type placed in a power transmission system. Typical clutch systems include a clutch basket rotationally coupled to a clutch input, a center clutch rotationally coupled to a clutch output, and one or more plates making up a clutch pack disposed between the clutch basket and center clutch. 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. 
         [0003]    Clutch packs are typically comprised of a plurality of two types of plates, friction plates and separator plates, where the separator plates are interleaved between the friction plates. In general, friction plates are coupled to the clutch input and separator plates are coupled to the clutch output, but in some cases, friction plates can be coupled to the clutch output and separator plates can be coupled to the clutch input. 
         [0004]    Friction plates typically have friction material affixed to either side with the friction material arranged symmetrically around the friction plate maintaining a relative concentricity with the friction plate. The friction material typically maintains a consistent working inner diameter and working outer diameter placing the friction material in direct contact with the opposing surface of a separator plate. 
         [0005]    In general, separator plates are round discs in structure and are designed to have a continuous and constant engaged surface for the friction material of the friction plate to contact. Typically, the engaged surface of the separator plate is defined by the annulus created by the working outer diameter and working inner diameter of the friction material so that the separator plate fully supports the inner and outer working boundaries of the friction material. 
         [0006]    Typically, such clutch systems include a clutch disengagement system consisting of a lever mechanically coupled to the pressure plate such that when the 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 lever to the pressure plate mechanically through a hydraulic actuation system or a cable actuation system. 
         [0007]    Most motorcycles incorporate a manual transmission coupled to the engine via a multi-plate clutch assembly. Typically, the multi-plate clutch operates in a wet environment where oil is used to help cool the clutch and provide lubricity in order to maintain consistent frictional performance. Typically, the multi-plate clutch is engaged/disengaged by the driver via a lever mounted on the handlebar. Although the lever operated clutch allows the driver to control the clutch engagement/disengagement, motorcycle drivers may find the clutch lever difficult to operate smoothly. Some of the difficulty associated with operating a clutch lever comes from changes in temperature causing thermal expansion and contraction of the clutch pack directly affecting the modulation point and lever modulation range. 
         [0008]    The modulation point is the lever position such that the clutch is disengaged when pulling the lever in from its resting position, or conversely where the clutch begins to re-engage when letting the lever out after the lever has been pulled in past the modulation point. 
         [0009]    The lever modulation range is the effective total distance the lever must be moved between the initiation point and lever modulation point. 
         [0010]    The initiation point corresponds to the lever position such that the pressure plate begins to move and the compressive force from the pressure plate begins to be removed from the clutch pack and thus clutch disengagement begins. Conversely, the initiation point corresponds to the lever position where the clutch fully re-engages when releasing the lever after it has been pulled in past the initiation point, modulation point, or some position between the initiation point and modulation point. 
         [0011]    Motorcycle riders have difficulty adjusting to changes in the lever modulation point and lever modulation range while applying the throttle and releasing the lever to engage the clutch and move the vehicle from a standing start. There are other situations where having to adapt to changes in the modulation point and lever modulation range makes controlling the clutch engagement or disengagement more difficult. Experienced motorcycle 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 while applying the throttle to maximize acceleration. 
         [0012]    Beyond clutch pack expansion and contraction due to temperature changes, the modulation point and lever modulation range can be affected by clutch drag that exists between adjacent faces of a friction plate and separator plate when both are rotationally coupled. Specifically, in a wet clutch, an oil film exists between the friction material and engaged surface of an adjacent separator plate. As the lever is actuated through the lever modulation range, pressure is reduced in the clutch pack lowering the coupling force between the friction material and engaged surface. Once the lever is pulled in to the lever modulation point, the oil film between the friction material and engaged surface must be sheared to de-couple the friction plate and separator plate. The surface tension of the oil is the oils ability to resist shearing under this condition and is affected by an oils construction and the oils temperature. The force required to shear the oil film can retard the engagement of the clutch and add undesirable drag to the clutch system; further hindering the feeling of the modulation point and making the clutch more difficult to control for the rider. 
         [0013]    Therefore a need exists for a separator plate that can dissipate more heat to aid in maintaining thermal stability of a clutch pack and improve the shearing of the oil film between the friction and separator plates to reduce clutch drag and improve the feeling of the modulation point. 
         [0014]    It is therefore an object of the present invention to provide a separator plate design that improves thermal stability, reduces the effect of the oil film&#39;s surface tension and improve the stability of the modulation point and allow the modulation range to remain consistent. 
         [0015]    The present invention for typical multi-plate clutch is disclosed in  FIGS. 1 through 5 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a view of a friction plate and separator plate. 
           [0017]      FIG. 2  is an isometric section view of a clutch pack. 
           [0018]      FIG. 3  shows the working annular area of contact between a friction plate and separator plate with inner and outer diameters denoted. 
           [0019]      FIG. 4  shows a standard separator plate 
           [0020]      FIG. 5  is of the preferred embodiment of a separator plate. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    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. 
         [0022]    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. 
         [0023]    Multi-plate clutch systems are well known in the art and are typified by systems included on motorcycles such as those provided by Honda such as the Honda model year 2008 CRF450R. 
         [0024]    A typical multi-plate clutch system includes a clutch basket, a center clutch, a clutch pack, a pressure plate, a compressive force mechanism, a disengagement mechanism, and a clutch lever. 
         [0025]    The typical multi-plate clutch is configured with the clutch basket being rotationally coupled to a clutch input, the center clutch being rotationally coupled to a clutch output, the clutch pack disposed between the clutch basket, center clutch and pressure plate where the compressive force mechanism acts on the pressure plate and the disengagement mechanism is disposed between the clutch lever and pressure plate. The center clutch and clutch basket are positioned concentrically about the same center. 
         [0026]    When the clutch pack is compressed, the clutch input and clutch output become rotationally coupled placing the multi-plate clutch in an engaged state. When the clutch is not compressed, the clutch input and clutch output are not rotationally coupled placing the multi-plate clutch in a disengaged state. The clutch pack is compressed by the pressure plate; the pressure plate being acted on by the compressive force mechanism. The disengagement mechanism, being disposed between the clutch lever and pressure plate, provides movement of the pressure plate when the clutch lever is actuated. In one direction, clutch lever actuation counter acts the compressive force mechanism and moves the pressure plate away from the clutch pack placing the multi-plate clutch in the disengaged state. When releasing the lever the pressure plate returns towards the clutch pack allowing the compressive force mechanism to compress the clutch pack through the pressure plate, placing the multi-plate clutch in the engaged state. 
         [0027]    The clutch pack typically consists of a plurality of friction plates and separator plates which are interleaved resulting in a separator plate between each friction plate. The friction plates contain features which rotationally couple the friction plates to the clutch basket. The separator plates contain features which couple the separator plates rotationally to the center clutch. 
         [0028]    Friction plates typically have friction material affixed to either side with the friction material arranged symmetrically around the friction plate maintaining a relative concentricity with the friction plate. The friction material typically maintains a consistent working inner diameter and working outer diameter placing the friction material in direct contact with the opposing surface of a separator plate. 
         [0029]    In general, separator plates are round discs in structure and are designed to have a continuous and constant engaged surface for the friction material of the friction plate to contact. Typically, the engaged surface of the separator plate is defined by the annulus created by the working outer diameter and working inner diameter of the friction material so that the separator plate fully supports the inner and outer working boundaries of the friction material. 
         [0030]    When the clutch lever is actuated in a manner to transition the multi-plate clutch from the engaged state to the disengaged state, there is an amount of clutch lever movement required called lever modulation range. The lever modulation range is defined by two points, the initiation point and modulation point. 
         [0031]    In the disengaging direction, the initiation point corresponds to the clutch lever position where the pressure plate first begins to move and any further clutch lever movement further reduces the net compressive force imposed on the clutch pack via the compressive force mechanism. Conversely, the initiation point corresponds to the clutch lever position where the multi-plate clutch fully engages when releasing the clutch lever after it has been actuated past the initiation point, modulation point, or some position between the initiation point and modulation point. 
         [0032]    The modulation point is the clutch lever position where the multi-plate clutch disengages completely when actuating the clutch lever in the disengaging direction. Conversely, the modulation point corresponds to the clutch lever position where the multi-plate clutch begins to re-engage when releasing the clutch lever after the clutch lever has been actuated in the disengaging direction past the modulation point. 
         [0033]    The modulation point shifts with changes in temperature caused by thermal expansion and contraction of the clutch pack thus shifting the lever modulation range. 
         [0034]    In addition to thermal induced shifting of the modulation point, the modulation point and lever modulation range can be affected by surface tension of the oil film that exists between adjacent faces of a friction plate and separator plate when both are rotationally coupled. Specifically, the oil film exists between the friction material and engaged surface of the adjacent separator plate. As the clutch lever is actuated through the lever modulation range, pressure is reduced in the clutch pack lowering the coupling force between the friction material and engaged surface. Once the clutch lever is pulled in to the modulation point the oil film between the friction material and engaged surface must be sheared to de-couple the friction plates and separator plates. The surface tension of the oil is the oils ability to resist shearing under this condition and is affected by an oils construction and the oils temperature. The force required to shear the oil film can add undesirable drag to the clutch system further increasing the lever modulation range and obscuring the modulation point. 
         [0035]    The present invention provides for a novel separator plate providing improved thermal stability for a multi-plate clutch system while reducing undesirable drag resulting in improved clutch lever control of the disengagement and engagement of a multi-plate clutch. Multiple embodiments are disclosed for separator plates to be used in a multi-plate clutch system. 
         [0036]      FIG. 1  discloses a typical prior art friction plate  101  and separator plate  102  from a multi-plate clutch. The friction plate  101  has a plurality of outer tabs  107 . The friction plate  101  has friction material  103  configured as a plurality of pads  104  arranged symmetrically around the friction plate  101  equidistant from the center of the friction plate  101  creating a friction inner boundary  105  and friction outer boundary  106 . The standard separator plate  102  is defined by the circular outer edge  110  and internal profile  111  where the internal profile  111  contains a plurality of indexing teeth  112 . 
         [0037]      FIG. 2  represents a clutch pack  200  from a multi-plate clutch. The clutch pack  200  being comprised of multiple friction plates  101  and standard separator plates  102  arranged in alternating fashion as typified by the prior art.  FIG. 2  shows the friction plates  101  and standard separator plates  102  stacked in alternating fashion with standard separator plates  102  positioned between each friction plate  101 . As typified by the prior art, the friction plates  101  are concentrically aligned with the separator plates  102 . In addition, the friction plates  101  have friction material  103  arranged on both sides signified by side one  201  and side two  202 . Side one  201  and side two  202  illustrate the contact between a friction plate  101  and adjacent separator plates  102  stacked on either side of a friction plate  101 . 
         [0038]      FIG. 3  discloses the working annulus  300 . The working annulus  300  has an inner diameter  301  and outer diameter  302 . The inner diameter  301  is defined by the working diameter of a circle tangent to the friction inner boundary  105  and concentric to the friction plate  101 . The outer diameter  302  is defined by the working diameter of a circle tangent to the friction outer boundary  106  and concentric to the friction plate  101 . The working annulus  300  represents the area where contact between a friction plate  101  and an adjacent separator plate  102  can take place. 
         [0039]      FIG. 4  depicts the standard separator plate  102  with inner diameter  301  and outer diameter  302  of the working annulus  300  projected onto the standard separator plate  102 .  FIG. 4  also shows the standard engaged area  400  of the standard separator plate  102 . The standard engaged area  400  is defined by the available area of the standard separator plate  102  within the working annulus  300  and thus in contact with the friction plate  101  when arranged in a multi-plate clutch. 
         [0040]      FIG. 4  shows the standard engaged area  400 , of the standard separator plate  102 , is equal to the area within the working annulus  300 . 
         [0041]      FIG. 5  discloses a preferred embodiment of the novel separator plate  500  with the inner diameter  301  and outer diameter  302  of the working annulus  300  projected onto the separator plate  500 .  FIG. 5  also shows the wavy engaged area  520  of the separator plate  500 . The wavy engaged area  520  is defined by the available area of the separator plate  500  within the working annulus  300  and thus in contact with the friction plate  101  when arranged in a multi-plate clutch. 
         [0042]    In addition,  FIG. 5  discloses an external opening  501  interrupting the outer diameter of the annulus  302  and providing an opening of the separator plate  500  within the area defined by the working annulus  300  shown projected on the separator plate  500 .  FIG. 5  also shows an internal opening  502  providing an opening of the separator plate  500  within the area defined by the working annulus  300  shown projected on the separator plate  500 . 
         [0043]      FIG. 5  shows the external opening  501  is defined by a leading edge  510 , a transition  511  and trailing edge  512  where the leading edge  510  and trailing edge  512  are asymmetric and are of non-equal edge lengths with respect to center line  513 . The internal opening  502  is defined by an internal leading edge  514 , internal transition  515 , and internal trailing edge  516  where the internal leading edge  514  and internal trailing edge  516  are asymmetric and non-equal edge lengths with respect to second center line  517 . 
         [0044]    As depicted in  FIG. 5 , leading edge  510  forms a curve which transitions from and is tangent to the outer edge  518  and connects and is tangent to the transition  511 . The transition  511  forms a curve which transitions from and is tangent to the leading edge  510  and connects and is tangent to the trailing edge  512 . The trailing edge  512  forms a curve which transitions from and is tangent to the transition  511  and connects to and is tangent to the outer edge  518 . Similarly, internal leading edge  514  forms a curve which transitions from and is tangent to the internal profile  519  and connects and is tangent to the internal transition  515 . The internal transition  515  forms a curve which transitions from and is tangent to the internal leading edge  514  and connects and is tangent to the internal trailing edge  516 . The internal trailing edge  516  forms a curve which transitions from and is tangent to the internal transition  515  and connects and is tangent to the internal profile  519 . 
         [0045]    In another embodiment leading edge  510  and trailing edge  512  are mirrored and symmetric with respect to center line  513 . In another embodiment internal leading edge  514  and internal trailing edge  516  are mirrored and symmetric with respect to second center line  517 . 
         [0046]    The separator plate  500  disclosed in  FIG. 5  shows six external openings  501  and six internal openings  502  arranged in alternating fashion distributed evenly around separator plate  500  maintaining symmetry relative to the working annulus  300  and centroid of the separator plate  500 . In another embodiment separator plate  500  has fewer external openings and fewer internal openings. In another embodiment separator plate  500  has external openings  501  and no internal openings  502 . In another embodiment separator plate  500  has internal openings  502  and no external openings  501 . In another embodiment the external opening  501  is smaller in size with differently shaped leading edge  510 , transition  511  and trailing edge  512 . 
         [0047]    In testing, the preferred embodiment of the separator plate  500  has increased thermal stability and reduced clutch drag when compared to the standard separator plate  102 . The wavy engaged area  520  of the separator plate  500  is reduced from the engaged area  400  of the standard separator plate  102  depicted in  FIG. 4 . The reduced area engaged between adjacent surfaces of the separator plate  500  and friction plate  101  lowers the drag due to oil film surface tension and provides a narrower modulation range when compared to a similar multi-plate clutch utilizing standard separator plates  102 . Furthermore, as the clutch is engaging the external opening  501  and internal opening  502  help to shear oil off of the friction pads  104  lowering drag and providing for a narrower modulation range. 
         [0048]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, for one skilled in the art, the present invention could be adapted for use in other types of vehicles that use clutch disengagement systems. 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.