Abstract:
A continuously variable drive element ( 100 ) has its torque transmission separate from its belt-squeezing function. The torque transmission is provided by only a first and second torque transmission tower and the belt-squeezing function is provided only by first and second belt-squeezing features. The preload of a compression spring is remotely adjustable without the need of disassembling the drive element.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates generally to a primary clutch and more particularly to a primary clutch having a pre-load adjuster and a primary clutch which uses only two transmission towers and two belt squeezing features.  
           [0003]    2. Description of the Prior Art  
           [0004]    Primary clutches work off of centrifugal force and are typically connected to an engine crank shaft. As the engine rotates, flyweights, which are connected to a moveable sheave, want to rotate radially from the axis of a post. The flyweight does this because the center of gravity of the weight is above (away from the engine) its pivot point. As the engine speed increases, the centrifugal force of the flyweights increase, thereby pushing against a spider. The spider is fixed to the post and cannot move. The stationary sheave is also fixed to the post and cannot move. A cover is fastened to the moveable sheave and both have bushings in them to allow them to slide axially on the post. A compression spring pushes against the fixed spider on one end and the sliding cover on the other. The spring is the reaction member that returns the clutch to neutral and opposes the flyweight force. As the engine RPM increases, the centrifugal force of the flyweights increases and the force on the moveable sheave sliding axially on the shaft towards the stationary sheave increases. Once there is enough force, the flyweights overcome the compression spring and apply a side force through the moveable sheave on a V-belt. This force pinches the belt between the moveable sheave and the stationary sheave. Once enough belt force is created, the vehicle will begin to move (clutch engagement). The side force of the belt is equal to the flyweight force (parallel to the post axis) minus the spring force.  
           [0005]    It is often desirable to change the pre-load provided by the compression spring, or to change the flyweights, in order to adjust the side force on the belt. Once a user gets a compression spring/flyweight system that performs well, the user will usually change weights to raise or lower the engine RPM at wide open throttle. If the spring isn&#39;t changed, the engagement RPM will also change. Another method that a user could do is to put a shim between the spider and compression spring, thereby changing the preload force. Using the formula noted above, changing the weights will change the amount of side force on the belt. It is typically a time consuming and difficult process to change the flyweights. Similarly, to change the amount of preload on a spring usually requires disassembly to place the shim in position. The present invention addresses the problems associated with the prior art devices and provides for a simple and effective method of remotely changing the preload of the spring without disassembling the primary clutch.  
           [0006]    Also, current primary clutches typically use three or four sliding buttons and typically have the torque transmission and belt squeezing functions together.  
           [0007]    The present invention addresses the problems in the prior art and provides for a primary clutch which utilizes only two torque transmission towers and only two belt squeezing features to provide for a better primary clutch. Still further, the present invention provides for the separation of the torque transmission from the belt squeezing functions.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention is a continuously variable transmission drive element for mounting on an engine crank shaft and adapted for use in a belt-type continuously variable transmission operatively connected by an endless belt to a driven element, the drive element includes a post and a first, stationary sheave having a conically faced belt-contacting portion operatively connected to the post. A second moveable sheave has a conical faced belt-contacting portion and a housing operatively connected to the conical-faced portion. The housing also has first and second torque transmission towers, each tower defining a longitudinal path. The housing also includes only first and second belt-squeezing features. A connector is fixedly secured to the post, the connector has only a first and second torque transmission members and only a first and second belt-squeezing members. The torque transmission members are slidable in a longitudinal path of the towers. A compression spring is operatively connected to the moveable sheave to provide a biasing force tending to urge the moveable sheave away from the stationary sheave, where torque transmission is provided only by the first and second torque transmission towers and the first and second torque transmission members. The belt squeezing is provided only by the two belt-squeezing members and belt-squeezing features.  
           [0009]    In another embodiment, the invention is a continuously variable transmission drive element for mounting on an engine crankshaft and adapted for use in a belt-type continuously variable transmission operatively connected by an endless belt to a driven element. The drive element includes a post and a first, stationary sheave operatively connected to the post. A second, moveable sheave is coaxially mounted on the post. A connector is fixedly mounted to the post, wherein the connector and the second sheave operate to move the second sheave longitudinally along the post to provide for belt squeezing and also to transmit torque. A compression spring is operatively connected to the moveable sheave to provide a preload to bias the moveable sheave away from the stationary sheave. An adjuster is provided to remotely change the preload of the compression spring.  
           [0010]    In another embodiment, the invention is a continuously variable transmission drive element for mounting on an engine crankshaft and adapted for use in a belt-type continuously variable transmission operatively connected by an endless belt to a driven element. The drive element includes a post and a first, stationary sheave operatively connected to the post. A second, moveable sheave is coaxially mounted on the post. A connector is fixedly mounted to the post, wherein the connector and the second sheave operate to move the second sheave longitudinally along the post to provide for belt squeezing and also to transmit torque. A compression spring is operatively connected to the moveable sheave to provide a preload to bias the moveable sheave away from the stationary sheave. A means for adjusting the preload remotely is provided.  
           [0011]    In another embodiment, the invention is a method of changing a preload on a compression spring in a continuously variable transmission drive element. The drive element has a preload compression spring operatively connected to the moveable sheave to provide a preload bias to urge the moveable sheave away from the stationary sheave. The method includes assembling a drive element with a first preload on a spring. Then, the method includes moving a spring preload adjusting member to cause longitudinal movement of a spring contacting member, thereby changing the first preload to a second preload, wherein the moving of the spring adjusting member is done remotely, without disassembling the drive element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a perspective view of the primary clutch of the present invention;  
         [0013]    [0013]FIG. 2 is a cross-sectional view of the primary clutch shown in FIG. 1 taken generally along the lines  2 - 2 ;  
         [0014]    [0014]FIG. 3 is a cross-sectional view of the clutch shown in FIG. 1 taken generally along the lines  3 - 3 ;  
         [0015]    [0015]FIG. 4 is a perspective view of the primary clutch shown in FIG. 1, viewed from below;  
         [0016]    [0016]FIG. 5 is a side elevational view of the clutch shown in FIG. 1;  
         [0017]    [0017]FIG. 6 is an exploded perspective view of the clutch shown in FIG. 1;  
         [0018]    [0018]FIG. 7 is a perspective view of the adjuster and spider of the clutch shown in FIG. 1;  
         [0019]    [0019]FIG. 8 is an enlarged perspective view of the moveable sheave and spider of the clutch shown in FIG. 1;  
         [0020]    [0020]FIG. 9 is a cross-sectional view of the clutch, taken generally along the lines  3 - 3  as in FIG. 2, but showing the clutch in a second position; and  
         [0021]    [0021]FIG. 10 is a cross-sectional view taken generally along the lines  10 - 10  in FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    Referring to the drawing, wherein like numerals represent like parts throughout the several views, there is generally disclosed at  100  a primary clutch. The primary clutch has a moveable sheave  1  having a conical shaped belt-contacting portion  1   a . A post  2  is secured to the moveable sheave  1  by suitable means such as threading the post  2  on to the moveable sheave  1 , as shown in FIG. 2. It is of course understood that other suitable methods may be used to secure the post  2  securely to the moveable sheave  1 . The post  2  has a threaded section  2   a  for use in threadably securing a spider  5  thereto, as will be described more fully hereafter. The post  2  has a longitudinal bore  2   b  extending through the post  2 . The bore  2   b  is tapered at the bottom of the post  2  for use in connecting to a crank shaft of an engine. Just below the threaded portion  2   a , a shoulder  2   c  is formed in the post  2 . A moveable sheave  14  has a central opening  14   a  into which a bushing  24  is inserted. Two washers are positioned on top of the bushing  24 . The bushing  24  and moveable sheave  14  is placed on the post  2  and the spacers  23  are positioned on the shoulder  2   c . The moveable sheave  14  is slidable along the post  2 , below the shoulder  2   c . The moveable sheave  14  has a conical shaped, belt contacting surface  14   b  which, along with a conical shape  1   a , provides for the contact with an endless V-belt (not shown). The moveable sheave  14  has a housing, generally designated at  50 , that is operably connected to, and preferably integral with the conical shaped surface  14   b . Referring especially to FIGS. 6 and 8, the housing  50  includes two transmission towers  51 . The transmission towers  51  have side walls  51   a  and  51   b  connected by an intermediate wall  51   c  to form a slot  51   d  that extends in a direction generally perpendicular to the longitudinal axis of the post  2 . Suitable reinforcing members  51  e are connected to the transmission towers to strengthen the towers  51 , as is well known in the art. Four mounting posts  52  are formed as part of the housing  50  and have threaded openings  52   a . Extending between the post  52  is a reinforcing member  53 . The moveable sheave  14  is symmetrical and only one of the reinforcing members will be described in detail as the other is a mirror image thereof. The reinforcing member  53  spans the distance between two posts  52  and forms a three-sided pocket  54 . A pair of openings  55  are formed in the pocket  54  and are used for mounting a flyweight  4  as will be described in more detail hereafter.  
         [0023]    The flyweight  4  has a curved section  4   a  operatively connected to a cylindrical section  4   b . A bore  4   c  extends through the cylindrical section  4   b . A spacer  26  is positioned inside of the bore  4   c . The cylindrical section  4   b  is placed inside of the pocket  54 . Washers  25  are positioned between the cylindrical section  4   b  and the pocket  54 . A pin  3  having a threaded end  3   a  is inserted through the opening  55  and through the cylindrical bore  4   c  and the flyweight is secured in position by a nut  27 . The flyweight is free to rotate on the bolt  3  and spacer  26  as it is being acted upon by centrifugal force. A connector or spider  15  has a housing generally designated at  15   a  which includes a base  15   b  which has a circular opening  15   c  formed therein. Extending below the circular opening  15   c  is a threaded segment which is threaded on to the threaded portion  2   a  of the post  2 , thereby securing the spider  15  to the post  2 . A side member  15   e  is operatively connected to the base  15   b . The side member  15   e  is continuous and forms a completed wall. There are two openings  15   f  formed in the side member  15   e . The openings  15   f  are spaced at 180 degrees from each other and are positioned to allow the end of the flyweight  4  to not hit the spider side member  15   e  when the flyweights  4  are raised. Two transmission members  15   g  are operatively connected to and extend from the side member  15   e . The transmission members  15   g  are spaced 180 degrees from each other, although it is understood other spacings may also be used. Formed in the transmission members  15   g  is an opening  15   h . A roller  8  is positioned in the opening  15   h  and is secured by a pin  7  which extends through an opening  15   j  and into a bore formed in the roller  8 . The pin  19  is inserted into an opening  56 , as seen in FIG. 10, and extends to and contacts a recess  7   a  formed in the pin  7 . The pin  19  forms a friction fit and thereby secures the pin  7  and roller  8  inside of the transmission members  15   g . Spaced 90 degrees from the transmission members  15   g  are two belt-squeezing members  15   k , although it is understood other spacings may also be used. The belt-squeezing members  15   k  are spaced 180 degrees from each other and extend from the side member  15   e . The belt-squeezing members  15   k  are in the general shape of an inverted U-shaped channel, the end of which is open. Openings  15   m  are formed on each side of the U-shaped channel. Positioned inside of the U-shaped channel is a roller  5  which has a longitudinal bore extending there through into which a bushing  21  is positioned. The roller  5  is then positioned inside of the U-shaped channel with two washers on each side. Then, a pin  6  is inserted through the openings  15   m  and is secured by a nut  22 . While the preferred embodiment utilizes a spider  15  as a connector, it is understood that suitable connectors of the post to the moveable sheave may be utilized.  
         [0024]    A compression spring  9 , for providing a preload, to bias the moveable sheave away from the stationary sheave, is positioned with a first end resting on the base  15   b  of the spider  15 . A circular adjusting plate  11  has a central opening  11   a  formed therein. The opening  11   a  is sized to fit over the post  2 . A circular flange member  11   b  extends around the base of the adjuster plate  11 . The flange  1   b  is sized and configured to fit inside of the threaded pathway  10   a  of a cam or cap  10 . As will be described more fully hereafter, as the cam  10  is rotated, the adjuster plate will move up and down, based on the rotation of the cam. At the base of the cam  10  is a plurality of straight segments  10   b  which are operatively connected to and form a base for the cam  10 . The segments  10   b  create gripping areas for a wrench or other tool to rotate the cam  10 . A cover  13  is secured to the moveable sheave  14  by four bolts  16  and washers  17  to the threaded openings  52   a  of the mounting posts  52 . The cover has a recess in which the cam  10  is positioned. The cover  13  has an opening  13   a  in which a bearing  18  is positioned. The bearing  18  is positioned around the post  2 . A pin  12  is fixedly secured to the underneath side of the cover  13 . The pin  12  extends through a cutout  1   b  in the adjuster plate  11 . This pin prevents the rotation of the adjuster plate  11 . It is of course understood that other suitable methods of doing so may be utilized.  
         [0025]    While the embodiment thus far described utilizes a cover plate, it is understood that other clutches may be of a different design and still utilize the present invention. The cover  13  is secured to the moveable sheave  14  and provides a means for allowing the compression spring to bias the moveable sheave  14  away from the stationary sheave  1 . Other constructions could also be utilized wherein a compression spring is used to provide the preload but with a different configuration. For example, a moveable sheave could have a housing which extends upward along the post. A compression spring would be positioned between the top of the housing of the moveable sheave and a shoulder which would be formed on the post. Thereby, the compression spring would have one end resting on the shoulder on the post and the other end urging the moveable sheave upward through its housing member. The present invention could still be utilized to remotely adjust the compression spring of this or other constructions of clutches.  
         [0026]    In operation, the primary clutch  100  begins in the position as shown in FIG. 3. Then, as rotation of the engine crankshaft causes rotation of the primary clutch as previously described, the flyweights  4  begin to pivot upward, around pin  3  because of centrifugal force. As the flyweights  4  move upward, the flyweight  4  contacts the roller  5  of the spider  15  and pushes on the spider  15 . Since the spider  15  is fixed to the post  2 , this moves the moveable sheave  14  downward, as shown in FIG. 9. The force of the flyweights  4  overcome the preload of the compression spring  9 . In doing so, the movement together the two conical-shaped surfaces  1   a  and  14   b  provide for a belt-squeezing force on the V-shaped belt and the vehicle will again begin to move as the clutch has now become engaged. The belt-squeezing force is provided by the combination of the flyweight  4  attached to the moveable sheave  14  and contact with the roller  5 , which is operatively connected to the spider  15 . All of the side belt force is created by the pair of belt-squeezing members. The torque transmission, on the other hand, is provided by the two rollers  8  in the spider  15  positioned in the transmission towers  51 . As the moveable sleeve  14  moves axially on the post  2 , the rollers  8  move inside of the slots  51   d . All of the torque transmission is provided by these pair of 180 degrees opposing rollers to the torque transmission towers  51 . It can therefore be seen that the transfer of torque and the belt-squeezing force are applied separately and through separate and distinct components of the primary clutch  100 . Further, the torque transmission and the belt side force are created by only two members. There are two rollers  8  for transmitting the torque and two flyweights  4  for the belt side force. The use of only two points is a significant benefit over the prior art which uses three or four or more point button system in which there are three or four points of contact to transmit torque. Then, you basically get a third bearing surface. During production settings, it is next to impossible to get the three bearing surface consistently coaxial. The three bearing surfaces are misaligned and binding can occur which creates a drop in clutch performance. The two points of contact of the present design will not act as a third bearing surface and will open up manufacturing tolerances, eliminate binding, allow the continuous variable transmission to react faster, have a longer life and be more efficient. The use of the two flyweights  4  instead of three or four or more allows for a freer running clutch with less drag and also provides for a lighter clutch. It is of course understood that other suitable methods of providing torque-power transmission and the belt-squeezing function may be utilized as are well known in the art. However, in one embodiment of the present invention, it is important that only two components and not the standard three or four or more components as is known in the prior art.  
         [0027]    As previously stated, users will typically adjust or tune their clutch by changing the compression springs or changing flyweights. With the present invention, the tuning of the clutch is very easily made and also can be made in finer increments. To change the preload on the compression spring  9 , it is only necessary to rotate the cam  10 , thereby causing the adjuster plate  11  to move closer to or away from the end of the spring  9 . This allows the spring  9  to either be compressed further or to become uncompressed, thereby changing the preload. As can be seen in FIG. 4, the surfaces  10   b  are readily available and the user can easily insert a wrench into the opening between the mounting post  52  to rotate the cam  10 , thereby adjusting the preload. It is of course understood that other suitable adjustment mechanisms may be used to remotely change the compression force of the spring  9 . When the term “remotely” is used in the present application, it is referring to changing the compression spring force without disassembly of the primary clutch  10 . This makes it very convenient to adjust the compression spring force  9  when out in the cold as snowmobilers typically are. Further, since the compression spring force is able to be changed so easily, one can change it during the day easily as temperatures rise or fall, thereby effecting how the user would want to tune the clutch.  
         [0028]    While the remotely adjusting of the preload has been described with respect to a cam and an adjuster plate that moves within the cam, it is understood that other suitable adjustments may be utilized. For instance, the cam  10  and adjuster plate  111  may be simply replaced with a cap with a threaded exterior. The threaded exterior could then be threaded on to the underneath side of the cover. The top of the spring  9  would bear against the cap and as the cap is rotated in its thread, the spring&#39;s preload would be adjusted. Still another method would be to have a sliding member with a ratcheting mechanism attached thereto. A ratchet mechanism could be constructed to cooperate with an adjuster plate. A pry bar or similar tool could be inserted into the ratchet mechanism to raise or lower the adjuster plate. A suitable locking mechanism could be utilized to lock the ratchet mechanism in position after the desired preload has been accomplished.  
         [0029]    The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.