Abstract:
An improved multi-disc wet clutch assembly. The improvements include an inner clutch hub having eighteen holes extending through a wall of the inner clutch hub, arranged in six series of three holes with each series being disposed approximately sixty degrees apart from each other and starting at a different position along the length of the inner clutch hub wall. The improvements further include a diaphragm plate disposed within a bore at the distal end of the inner clutch hub. Methods of retrofitting preexisting clutch assemblies are also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 62/280,466, filed on Jan. 19, 2016, the teachings of which are expressly incorporated by reference. 
     
    
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND 
       [0003]    The present disclosure relates generally to improved clutch systems, and more particularly to clutch systems featuring a plurality of ported oiling holes in the inner hub and a control diaphragm to contain the oil. 
         [0004]    In general, multi-disc wet clutch transmissions have a plurality of friction plates capable of engaging with one another. Transmissions that utilize a multi-disc wet clutch system typically have a limited amount of clutch allocated lubricant (oil) volume. This limited volume must be used in the most efficient and direct point placement to minimize the consumption of volume from the pump system that provides pressure and volume to the entirety of the transmission demands for gear and bearing lubrication. Typically the inner clutch hub is a forged or cast shape ported with oil from one side. This oil that is ported in, flows across inner hub and cools the inner surface profile of the clutch hub. With inadequate lubricant placement or volume, multi-disc wet clutch systems will run near dry, overheat, and cause friction material failure. 
         [0005]    In order to overcome these problems, various solutions have been introduced. For example, some designs have fluid holes drilled through the inner hub to allow a small percentage of the oil to centrifugally pass directly into the clutch plates. In this scenario, a majority of the oil is expelled out the large opening due to the design aspect and the lofted interior surfaces created for the mold/production and part ejection process during manufacturing. In many other applications, the clutch assembly actually sits in an oil bath or is sprayed from a port or ports to the outer surface of the clutch assembly. As elevated rpm is introduced, the clutch assembly cuts through the oil creating parasitic friction loss, foaming, and lubrication is centrifugally thrown off. 
         [0006]    As such, there is a need for a system to continuously oil and cool a wet clutch system at all engagement or modulation rpm ranges with a limited amount of lubricant volume. There is a need for such a system that allows for every friction plate to be sufficiently lubricated, while also minimizing system drag, parasitic friction loss, foaming, and other undesirable effects from the use of excess lubricant. 
       BRIEF SUMMARY 
       [0007]    The present disclosure contemplates an improved clutch assembly, by either modifying an existing multi-disc wet clutch assembly, or providing the improved clutch assembly outright. In the case of modifying an existing multi-disc wet clutch assembly, the amount of work required to significantly improve existing clutch assemblies requires only a few changes made to the central clutch hub (direct ported oiling holes), along with the addition of a control diaphragm installed within the assembly. 
         [0008]    This diaphragm system or fluid wall with an array of direct ported oiling holes through the inner clutch hub is capable of maintaining control of nearly 100% of the small volume of oil ported to the center of the clutch hub. This oil now can be directed through every friction plate and steel plate, thereby maximizing the efficiency of the small volume in cooling and lubrication of the clutch assembly. Furthermore, even as RPM is increased, the oil path is always the same, and must pass between the clutch plates. As such, it can be seen that the improved clutch assembly of the present disclosure is greatly improved over the known prior art. In accordance with one embodiment of the present disclosure, there is contemplated an improved multi-disc wet clutch assembly made up of an outer clutch basket having a plurality of friction plates contained within and operably connected to the outer clutch basket. 
         [0009]    The assembly further includes an inner clutch hub having an outwardly extending base portion at a proximal end and a plurality of standoff posts extending outwardly from a distal end. The inner clutch hub is rotatably disposed within the outer clutch basket. Furthermore, the inner clutch hub includes eighteen holes extending through a wall of the inner clutch hub. The holes are arranged in six series of three holes along the length of the inner clutch hub wall with each series being disposed approximately sixty degrees apart from each other and each series starting at a different position along the length of the inner clutch hub wall. 
         [0010]    The assembly further includes a plurality of clutch plates disposed around and operably connected to the inner clutch hub. The plurality of friction plates and plurality of clutch plates are alternately overlapped with each other. 
         [0011]    The assembly further includes a pressure plate disposed along the plurality of standoff posts and sandwiching the plurality of friction plates and plurality of clutch plates with the inner clutch hub base portion. The assembly further includes a pressure plate spring abutting the pressure plate. 
         [0012]    The assembly further includes a diaphragm plate disposed along the plurality of standoff posts and within a bore located at the distal end of the inner clutch hub. The assembly contains a diaphragm O-ring disposed between the diaphragm plate and the inner clutch hub and three diaphragm springs disposed along three stand-off posts located approximately one hundred twenty degrees apart from each other between the diaphragm plate and the pressure plate. 
         [0013]    Another embodiment of the present disclosure envisions a method for improving a multi-disc wet clutch assembly. The assembly has an outer clutch basket and a plurality of friction plates contained within and operably connected to the outer clutch basket. The assembly further includes an inner clutch hub having an outwardly extending base portion at a proximal end and a plurality of standoff posts extending outwardly from a distal end. The inner clutch hub is rotatably disposed within the outer clutch basket. The assembly also includes a plurality of clutch plates disposed around and operably connected to the inner clutch hub. The plurality of friction plates and plurality of clutch plates alternately overlap each other. The assembly further includes a pressure plate disposed along the plurality of stand-off posts and sandwiching the plurality of friction plates and plurality of clutch plates with the inner clutch hub base portion and a pressure plate spring abutting the pressure plate. 
         [0014]    The method includes a step of forming a concentric bore at the distal end of the inner clutch hub. The bore may be formed approximately half an inch deep. A diaphragm plate is then placed within the bore and along the plurality of standoff posts with an O-ring positioned between the diaphragm plate and the inner clutch hub. Additionally, at least one spring is positioned between the diaphragm plate and the pressure plate. In that regard, three springs may be placed between the diaphragm plate and the pressure plate. The springs may be placed along the standoff posts. 
         [0015]    The method also includes a step of forming a plurality of holes through a wall of the inner clutch hub. In that regard, eighteen holes may be formed through the wall of the inner clutch hub. Further, the holes may be arranged in six series of three holes along the length of the inner clutch hub wall. Additionally, each series of holes may be formed approximately sixty degrees apart from each other. Also, each series of holes may be formed such that each series starts at a different position along the length of the inner clutch hub wall. 
         [0016]    The method may be used with forged or cast inner clutch hubs. 
         [0017]    Yet another embodiment of the present disclosure envisions an improved multi-disc wet clutch assembly having an outer clutch basket and a plurality of friction plates contained within and operably connected to the outer clutch basket. 
         [0018]    This assembly also includes an inner clutch hub having an outwardly extending base portion at a proximal end and a plurality of standoff posts extending outwardly from a distal end. The inner clutch hub is rotatably disposed within the outer clutch basket and includes a plurality of holes extending through a wall of the inner clutch hub. 
         [0019]    Further, this assembly includes a plurality of clutch plates disposed around and operably connected to the inner clutch hub, such that the plurality of friction plates and plurality of clutch plates are alternately overlapped with each other. 
         [0020]    This assembly also includes a pressure plate disposed along the plurality of stand-off posts and sandwiching the plurality of friction plates and plurality of clutch plates with the inner clutch hub base portion and a pressure plate spring abutting the pressure plate. 
         [0021]    In addition, this assembly includes a diaphragm plate disposed along the plurality of stand-off posts and within a bore located at the distal end of the inner clutch hub with a diaphragm O-ring disposed between the diaphragm plate and the inner clutch hub. Additionally, there is at least one diaphragm spring disposed along at least one standoff post between the diaphragm plate and the pressure plate. 
         [0022]    There may be eighteen holes extending through the wall of the inner clutch hub in this embodiment. Furthermore, the holes may be arranged in six series of three holes along the length of the inner clutch hub wall. Also, each series of holes may be disposed approximately sixty degrees apart from each other. Additionally, each series may start at a different position along the length of the inner clutch hub wall. 
         [0023]    In this embodiment, there may be three diaphragm springs located approximately one hundred twenty degrees apart from each other and the inner clutch hub may be a forged or cast shape. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
           [0025]      FIG. 1  is an exploded side view of a clutch assembly of the present disclosure; 
           [0026]      FIG. 2  is a top view of the clutch assembly shown in  FIG. 1 ; 
           [0027]      FIG. 3  is a bottom view of the clutch assembly shown in  FIG. 1 ; 
           [0028]      FIG. 4  is an assembled side view of the clutch assembly shown in  FIG. 1 ; 
           [0029]      FIG. 5  is a cross-sectional view of the clutch assembly shown in  FIG. 4  along line  5 - 5 ; and 
           [0030]      FIG. 6  is a detailed cross-sectional view of the clutch assembly shown in  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    The detailed description set forth below is intended as a description of the presently preferred embodiment of the invention, and is not intended to represent the only form in which the present invention may be constructed or utilized. The description sets forth the functions and sequences of steps for constructing and operating the invention. It is to be understood, however, that the same or equivalent functions and sequences may be accomplished by different embodiments and that they are also intended to be encompassed within the scope of the invention. 
         [0032]    As shown in the Figures, there is an improved multi-disc wet clutch assembly  10 . This improved assembly  10  may be formed during its initial manufacture, or alternatively may be formed by modifying a preexisting clutch assembly. An example of the modification of a preexisting clutch assembly is described below. 
       Assembly of the Invention 
       [0033]    In order to outfit the existing clutch used in this assembly  10  from the 2016 Yamaha YXZ 1000R a concentric bore  12  was cut inside the central clutch hub  14  approximately half an inch deep to allow the diaphragm plate  16  and the O-ring  18  that goes around it to be slid into the central clutch hub  14 . The existing central clutch hub  14  appears to be a net forged unit or cast unit having an amount of loft on the interior profile. This existing loft is for release from the mold tooling in its manufacturing process. This loft in the first half-inch section was removed to provide reliable sealing of the diaphragm plate  16  and a mechanical stop point to control its location of depth in the clutch hub  14 . 
         [0034]    In this application, three low-pressure compression springs  20  were used in an even orientation of one hundred twenty degrees of separation, over the total three hundred sixty degrees. The springs  20  slide over the existing pressure plate standoff posts  22  made into the central clutch hub  14 . The springs  20  rest against the outer surface of the newly installed diaphragm plate  16  and pass through the existing pressure plate  24  with no modifications. The outside face of these three diaphragm retaining springs  20  are now retained by the interior surface of the unmodified pressure plate spring  26 . 
         [0035]    The unmodified pressure plate spring  26  is now bolted down to the central clutch hub  14  providing the original installation orientation and elevation. The use of the three springs  20  allows the original pressure plate  24  to be modulated in its entirety with the original clutch clamp pressure and continuously applies the small amount of force to retain the diaphragm plate&#39;s location and sealing. 
         [0036]    In this application the clutch  10  is oiled from the input shaft  28  that couples to the central clutch hub  14 . The shaft  28  is drilled and oil passes through its centerline  30 , in which it is plugged at the end of the shaft by the throwout bearing pin (not shown). This shaft  28  is cross drilled to provide pressurized oil lubrication provided from the transmissions oil pump to the thrust sealing bushing and roller bearing  32 . This allows for the rotational difference between the outer clutch basket  34  and the central clutch hub  14 . 
         [0037]    The expelled waste oil from this roller bearing  32  is directed out of the bearing  32  into a recessed pocket  36  made in the central clutch hub  14 . There is a negative taper machined into the central clutch hub pocket  36  that traps the expelled oil via centrifugal force. There is a series of six ports that are tangent to the large inner diameter of this negative taper in which the directed oil captured is forced through from the centrifugal force. This area in which the oil has passed through is now in the “new near sealed” interior cavity of the central clutch hub  14 , minus the newly drilled ports listed next. 
         [0038]    An array of eighteen holes  38  were drilled through the minor diameter of the drive splines for the clutch plates  42  on the central clutch hub  14 . This array for this particular central clutch hub  14  is sixty degrees apart and directly inline with each of the fluid ports listed above and is not critical on the exact orientation or count. There are three equally spaced holes  38  per the array used, with a different starting point from the front face of the central clutch hub  14  to provide an even distribution of oil and centrifugal head pressure across the depth of the multi-disc clutch pack  40 ,  42 . 
         [0039]    Before the modification to the inner clutch hub  14  and installation of the diaphragm plate  16 , there was only one 0.120 hole  44  through the central clutch hub  14  to the minor diameter of the drive splines for the clutch plates  42 . This hole  44  was used in this application for retention of a wire retaining ring to retain some of the inner clutch plates  42 , friction plates  40 , and some clutch disc separation springs (jitter springs). The flow path of the oil that entered this cavity follows the loft profile to the large opening in which the oil would be expelled out, only contacting the last couple clutch plates  42  adjacent to the pressure plate  24 . This system could not develop any form of head pressure to force oil through the single 0.120 hole  44  to cool and lubricate the clutch discs. 
         [0040]    In testing, comparing the data from the unmodified clutch assembly to the modified assembly  10  there was a documented six hundred degree temperature reduction of the clutch plates over a one hundred mile cycle on the same vehicle. This reduction of temperature has a direct effect on the life and reliability of the clutch/friction plates. 
         [0041]    In the improved clutch assembly as described herein, the use of a diaphragm with an array of direct ported oiling holes through the inner clutch hub now maintains control of nearly 100% of the small volume of oil ported to the center of the clutch hub. This oil flow can be seen by way of the arrows illustrated in  FIG. 6 . The diaphragm oil control plate  16  that is installed into the central clutch hub  14  is pressed in and O-ring sealed. It is held in position with small springs  20  placed between the diaphragm plate  16  and pressure plate  24 . The diaphragm plate, fluid wall, or even a sealed chamber (minus the array ports to the clutch disks) can be pressurized or rely on centrifugal force from the incoming fluid from the clutch shaft. 
         [0042]    Instead of modifying a preexisting clutch assembly to achieve this result, the design can be incorporated as an integral component in a net cast unit. This may also be retained by means of a bolted, press fit, threaded, snap ring or C-clip type attachment. The cavity created between the back wall of the inner clutch hub  14  and the diaphragm plate  16  can be filled to the elevation of the pressure plate standoff posts before any fluid can escape through any other path than the holes  38  through the clutch hub  14  to the discs  40 ,  42 . Rotation of the clutch assembly  10 , which is proportional to the engine or power source, causes centrifugal force inducing applied pressure to the drilled holes  38  in the clutch hub.  14  This again forces lubrication to the clutch and friction discs  40 ,  42  along this oil path, which remains a constant, and must pass between the clutch and frictions plates  40 ,  42 . 
         [0043]    As can be seen, this improved system provides many benefits over the prior art including, but not limited to: 
         [0044]    (1) Solving a need for accurate placement of a limited volume of oil for wet clutch units. 
         [0045]    (2) Very little modification or cost is needed to retrofit existing assemblies. 
         [0046]    (3) Providing continuous and reliable lubrication and cooling to multi-disc wet clutch units at any RPM, clutch position modulation, or load demand. 
         [0047]    (4) Capturing fluid and using centrifugal force as a means to pressurize lubricant through clutch plates and friction plates. 
         [0048]    (5) The design can be adapted to multiple clutch designs of single and multi-disc wet clutch systems. 
         [0049]    (6) It eliminates the need for a wet clutch to function in an oil bath or use an external spray system. 
         [0050]    (7) It eliminates parasitic loss from oil splash and foaming and adds a fluid shearing factor promoting rotational transfer between the clutch plates and friction plates. 
         [0051]    (8) It allows a clutch unit to be located well above the oil level of a transmission, or the oil level can be reduced in dry sump application transmissions. 
         [0052]    The above description is given by way of example, and not limitation. Given the above disclosure, one skilled in the art could devise variations that are within the scope and spirit of the invention disclosed herein, including using the improvements described in various types of clutch assemblies. Further, the various features of the embodiments disclosed herein can be used alone, or in varying combinations with each other and are not intended to be limited to the specific combination described herein. Thus, the scope of the claims is not to be limited by the illustrated embodiments.