Abstract:
A plate for a rocker joint chain in which the plate includes two longitudinal legs and two vertical legs that together enclose a plate opening. The plate includes at least one recess in a longitudinal leg to replace a tab that extends from a longitudinal leg in previously employed plates. A guide rail along which the rocker joint chain travels to reduce slack strand vibrations during chain movement is subject to less wear than with the previously employed plates.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plate for a rocker joint chain, wherein the plate includes two longitudinal legs and two vertical legs that together enclose a plate recess. 
     2. Description of the Related Art 
     A known rocker joint chain is disclosed in published German patent application DE 103 16 441 A1. That chain has sequentially arranged plates in a plurality of adjacent rows perpendicular to the direction of chain travel, and the plates in adjacent rows partially overlap and are connected by rocker members that extend into the plates in the direction perpendicular to the direction of chain travel. Two pairs of rocker members extend through a recess in each plate, and the outermost rocker members that face away from each other abut the front and rear inside surfaces of the plate recess. The innermost rocker members that face each other abut the front and rear inside surfaces of the recesses of adjacent plates. The facing surfaces of the rocker members of a rocker member pair roll against each other when the rocker joint chain transitions from a straight, extended form to a curved form. Such rocker joint chains are used in a variable speed drive unit of a belt-driven conical-pulley transmission, a so-called continuously variable transmission (CVT), for example. 
     The plates include tabs that are used to help assemble the rocker joint chain, and the tabs contact a guide rail of the CVT transmission in the event of strand vibration. Such guide rails are provided to limit the transverse vibrations of the rocker joint chain. As the torque increases, the strand vibrations increase in the CVT transmission. As a result, the tabs cause pitting in the guide rail when the transverse vibrations are high. 
     Guide rail wear also reduces the useful life of the rocker joint chain. An object of the present invention is therefore to provide plates that cause less wear of the chain guide rail in comparison with prior art plates. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the object is achieved with a plate for a rocker joint chain in which the plate includes two longitudinal legs and two vertical legs that together enclose a plate recess, wherein at least one recess is provided in at least one of the longitudinal legs. The purpose of the recess is similar to that of the previously used tabs, which is to help orient the plates when assembling the rocker joint chain. Instead of two downwardly extending tabs, one or a plurality of recesses are provided in the plate. That greatly increases the contact surface area between the outer contour of the plate and the guide rail. The recesses can be in both of the bottom and top longitudinal legs of the plate. Depending upon the method of assembly, both longitudinal legs (top and bottom) can be provided with recesses. 
     At the recess, the longitudinal leg preferably has a height “b” with reference to a baseline, and the recess has a depth “a” with reference to the baseline, wherein the ratio 
             0.1   ≤     a   b     ≤   0.5         
applies. Furthermore, the ratio is preferably
 
               a   b     =       1   5     .           
The baseline is a straight line that extends over the recess in the longitudinal leg. The baseline therefore corresponds to the outer edge surface of the longitudinal leg of the plate before the recess is formed, when it is formed by cutting, for example.
 
     It is preferable for the recess in the longitudinal profile of the plate to be trapezoidal or rectangular. The recess in the longitudinal profile of the plate is preferably trapezoidal with rounded corners or rectangular with rounded corners. The term “trapezoidal” is hence also understood to be a shape of the recess in which a trapezoid can be inserted so that it contacts in the contour of the recess at a plurality of points, at least three. The expression “rounded corners” is especially understood to mean contours that have smooth transitions between differently curved surfaces. 
     The recess is preferably formed by adjacent convex and concave curves that smoothly transition into each other and form a generally trapezoidal or rectangular recess. In one variation, concave curves joined by a section of a straight line are arranged on both sides of an axis of symmetry. The convex or concave curves are preferably defined by radii, and the radii can be equivalent. The recess in the longitudinal profile of the plate can alternately be shaped like a section of circle or the section of an ellipse. 
     In one embodiment of the invention, the recess is approximately in the middle relative to a centerline of the plate. In another embodiment, a plurality of recesses are arranged in a longitudinal leg, wherein the recesses are preferably arranged symmetrically relative to a centerline of the plate. 
     The earlier-identified object is also achieved with a rocker joint chain that at least partially includes plates having the configuration described above. 
     The earlier-identified object is also achieved with a variable speed drive transmission having a plate-link chain according in accordance with the present invention, wherein the recesses in the plates are on the side of the plates that are guided past a guideway of a guide rail during operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic representation of a known belt-driven conical pulley transmission with an associated control unit; 
         FIG. 2  is a cross-sectional view perpendicular to the axes of a known belt-driven conical pulley transmission; 
         FIG. 3  is a side view of a portion of a rocker joint chain; 
         FIG. 4  is an enlarged side view of a plate and rocker member; 
         FIG. 5  is a side view of a first exemplary embodiment of a plate in accordance with the present invention; 
         FIG. 6  is a side view of a second exemplary embodiment of a plate in accordance with the present invention; 
         FIG. 7  is an enlarged, fragmentary view of detail I of  FIG. 5 ; 
         FIG. 8  is an enlarged, fragmentary view of detail II of  FIG. 7 ; 
         FIG. 9  is an enlarged, fragmentary view showing the form of the construction of the contour of the recess shown in  FIG. 8 ; 
         FIG. 10  is a first sketch showing the length relationships of one form off the recess; 
         FIG. 11  is a second sketch showing the length relationships of another form of the recess; and 
         FIGS. 12   a - 12   e  show various alternative exemplary embodiments of the form of the recess. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A state-of-the-art variable speed drive transmission and rocker joint chain are explained with reference to  FIGS. 1 to 4  to provide a better understanding of the present invention and to illustrate the concepts that are applied. The variable speed drive transmission (a belt-driven conical-pulley transmission) includes two pairs of conical disks  1  and  4 . Conical disk  2  of conical disk pair  1  is rigidly connected to a drive shaft  7  that is driven by an internal combustion engine, for example. Conical disk  5  of the other conical disk pair  4  is rigidly connected to an output shaft  8  that drives the vehicle. The other conical disk  3  of the conical disk pair  1  is non-rotatably but axially movably connected to drive shaft  7 . The other conical disk  6  of the conical disk pair  4  is non-rotatably but axially movably connected to output shaft  8 . Passing around both conical disk pairs  1  and  4  is endless-torque transmitting means  9 , a rocker joint chain as shown in  FIG. 3 , for example, that frictionally engages the facing conical surfaces of the conical disk pairs. As a result of opposite adjustment of the axial spacing between the two conical disks of each conical disk pair the speed ratio between the two conical disk pairs can be changed, and hence the transmission ratio of the transmission. 
     To change the transmission ratio, pressure chambers  10  and  11  are connected by means of hydraulic lines  12  and  13  to a control valve unit  14  that can control the hydraulic fluid pressure supplied to the pressure chambers  10  and  11 . To control the control valve unit  14 , a control unit  15  is used that contains a microprocessor with associated memory devices, and its inputs are connected to a selector lever unit to actuate the transmission, a gas pedal, and speed sensors, for example, and its outputs are connected to a clutch, a power controlling element of the engine (not shown), and the control valve unit  14 , for example. The design and operation of such a belt-driven conical-pulley transmission are known and therefore will not be described further. 
       FIG. 2  shows a cross-sectional view perpendicular to the axes of shafts  7  and  8  through a belt-driven conical-pulley transmission, in which the slack strand of the endless torque transmitting means  9  is guided by a guide rail  16  that prevents the slack strand from vibrating. In the illustrated example, the direction of rotation of the disk pairs  1  and  4  is counter clockwise, and  7  is the drive shaft driven by the engine. The belt-driven conical-pulley transmission or its endless-torque transmitting means  9 , represented by dashed lines, is shown in two different positions. In one position A, the distance between the conical disks of the conical disk pair  1  is the minimum, and the distance between the conical disks of conical disk pair  4  is the maximum, so that the transmission operates at the highest possible transmission ratio. In another position B, the spacings between the respective disk pairs are reversed relative to those of position A, the transmission operates at the lowest possible transmission ratio, and the radius at which the endless-torque transmitting means circulates on the conical disk pair  4  is the maximum radius. 
     The guide rail  16  that guides the endless-torque transmitting means  9  between an outer guideway  18  and inner guideway  17  is mounted on a pin or oil pipe  19  that is affixed to the transmission housing (not shown). Guide rail  16  includes a substantially U-shaped seat  20  whose opposed side walls are approximately perpendicular to the direction of movement of the endless-torque transmitting means, or the longitudinal direction of the guide rail. Seat  20  is so formed that the guide rail follows the change of the path of movement of the endless-torque transmitting means  9  by pivoting on the oil pipe  19 , and by the movement of the opposed walls of the seat  20  on the outer surfaces of the oil pipe  20 , so that the loose strand of the endless-torque transmitting means is always securely guided and is secured against vibration. The oil pipe  19  has radial holes through which (and through corresponding recesses in the floor of the seat  20 ) the inside of the guide rail  16  is supplied with lubricant to lubricate the endless-torque transmitting means so that it is movable along the guide rail  16  with reduced friction. 
       FIG. 3  shows a portion of a rocker joint chain  22  that is composed of plates  21  that are connected with each other by means of rocker members  25 . The plates  21  are sequentially arranged in a plurality of longitudinally-extending rows that are adjacent relative to the direction of travel of the rocker joint chain  22 . In  FIG. 3  plate  21 . 1  belongs to the front row in the viewing direction, plate  21 . 2  belongs to the row neighboring the front row, and plate  21 . 3  belongs to another row. 
     To connect the plates, rocker members  25  are provided that extend into the plate openings  23  in a direction perpendicular to the direction of chain travel. Each plate opening is penetrated by two rocker member pairs  24 . 1  and  24 . 2 , wherein plates  21 . 1  and  21 . 2  are associated with rocker member pair  24 . 1 , and plates  21 . 1  and  21 . 3  are associated with rocker member pair  24 . 2 . As can be seen, the oppositely facing surfaces of the rocker members  25 . 1  and  25 . 4  facing away from each other of rocker member pairs  24 . 1  and  24 . 2  abut the front and rear inside surfaces, with reference to the direction of travel of the rocker joint chain  22 , of the plate opening  23 . The rocker members  25 . 2  and  25 . 3  that face each other abut the insides of plate openings in plates that are in neighboring rows. The facing surfaces of the rocker members of each rocker member pair form rolling surfaces at which the rocker members roll against each other given a change in the radius RL with which the respective portion of the rocker joint chain  22  curves. 
     Such a rocker joint chain  22  and the associated variable speed drive unit in  FIG. 1  and  FIG. 2 , with two conical disk pairs around which the rocker joint chain  22  circulates, are known and will therefore not be further described. 
       FIG. 4  shows an enlarged prior art plate  21  and a rocker member  25 . The rocker member  25  has two longitudinal legs  26  and two vertical legs  27  that together enclose the plate opening  23 . In  FIG. 4 , the rocker member  25 , whose rolling surface is identified as  28 , contacts the right side inner surface of the plate opening  23 , wherein the respective contact surfaces are adapted to each other such that contact only occurs at the transitions from the longitudinal legs  26  to the vertical legs  27 , and there is no contact in the middle of the vertical leg  27 . When the plate  21  in  FIG. 4  moves from right to left, a force corresponding with the force that is transmitted by the rocker joint chain  22  is transmitted to the contact surfaces, which force is indicated in the figure by the arrows F, which show the direction of the force. As a result of shifting the force application points toward the middle of the longitudinal legs, both tensile stresses and bending stresses act in the longitudinal legs  26 . Likewise, bending stresses and tensile stresses also act in the vertical legs. 
     The plate  21  includes tabs  29  on at least the outside of one of the longitudinal legs  26 . The tabs are identified in this instance by reference numerals  29 . 1  and  29 . 2 . The tabs  29  contact the inner guideway  17  or the outer guideway  18  when the strand of the rocker joint chain  20  vibrates, which causes pitting. Pitting involves the formation of micro-fissures close to the surface from the impacts of the tabs  29  on the surface of the guideway  17  or  18 . A stop tab  30  limits the maximum angular deflection of the plate-link chain, that is, radius RL in  FIG. 4 , because the stop tab contacts a neighboring plate. 
       FIGS. 5 and 6  show exemplary embodiments of a plate in accordance with the invention that has one or two recesses  31  instead of the tab  29 . In the exemplary embodiment shown in  FIG. 5 , a recess  31  is in the middle of the plate  21 ; the middle of the plate  21  is indicated by a centerline  36 .  FIG. 6  shows a second exemplary embodiment of a plate in accordance with the present invention that includes two recesses, identified by reference numerals  31 . 1  and  31 . 2 , which are on each side of the centerline  36 . When a plate in accordance with the present invention contacts one of the guideways  17  or  18 , the contact surface area is substantially larger than with the prior art plate because a large part of the surface of the respective longitudinal leg  26  contacts the guideway  17  or  18 , instead of individual tabs having a very small contact surface as in the prior art plates. 
     The recesses  31  can be provided in the bottom or top longitudinal leg  26 . The bottom longitudinal leg refers to the inner side of the rocker joint chain  22  when the rocker joint chain  22  is installed and encircles a conical disk pair, and the top longitudinal leg  26 , correspondingly, refers to the outer side of the rocker joint chain  22  when a conical disk pair is encircled. 
       FIG. 7  shows detail I of  FIG. 5 . The region of the recess  31  is shown in an enlarged view. At an axis of symmetry  32 , which in this case coincides with the centerline  36 , the longitudinal leg  26  has height “b” with reference to a baseline  33 . The baseline represents the outer contour of the longitudinal leg  26  that spans the recess  31 . The baseline  33  can be most easily represented as a straight line that tangentially contacts any two points of the longitudinal leg  26 , as if the plate  21  was placed on a flat panel. The depth of the recess  31  with reference to the baseline  33  is shown in  FIG. 7  as depth “a.” The following applies for the relationship between values “a” and “b”: 0.1≦a/b≦0.5. In a preferred embodiment, a:b=1:5. 
       FIG. 8  shows detail II of  FIG. 7  as a further enlarged representation of recess  31 . The recess shown in  FIG. 8  is one possible exemplary embodiment of the form of the recess. The basic shape of the recess  31  is in the general form of a trapezoid  34 , shown as a dot-dashed line in  FIG. 9 . The angles at the corners of the generally trapezoidal recess are curved corners that are approximated by tangential circles. For example, in  FIG. 9  two tangential circles K 1  and K 2  are shown that each tangentially contact the sides of trapezoid  34  at two points. For circle K 1 , those points are points T 1  and T 2 , and for circle K 2  those points are points T 2  and T 3 . In that manner, the trapezoidal shape is approximated by a series of circle segments that define circular arcs. 
     In the representation in  FIG. 9 , the two straight sections between points T 1  and T 2  are replaced by the circular arc that is a circle segment of circle K 1 , and is represented by a continuous line. Correspondingly, the two straight sections abutting each other between points T 2  and T 3  are replaced by the corresponding circular arc that is a circle segment of circle K 2 . In the present exemplary embodiment, the radii of circles K 1  and K 2  are identical, and in  FIG. 8  that is indicated by the same identification of the radii R. Alternatively, those radii can also be different. The forms of the contours contacting the trapezoid  34  are symmetrical to an axis of symmetry  32 . The circle segments lying to either side of the centerline  36  (in  FIG. 9 , one of those segments is the circle segment that is part of circle K 2 ) are thereby connected by a section of a straight line to yield the contour shown in  FIG. 8 . 
       FIG. 10  shows the geometric relationships of the lengths of individual sections of the trapezoid  34  shown in  FIG. 9 . The height of trapezoid  34  is identified by line “a” in  FIG. 9 , which corresponds to the depth “a” of the recess  31  shown in  FIG. 7 , and the lengths of the lines “c” and “d”, and the opening angle α of the leg. For the relationship between those values the following applies: 
     
       
         
           
             
               arctan 
               ⁡ 
               
                 ( 
                 
                   
                     2 
                     · 
                     a 
                   
                   
                     d 
                     - 
                     c 
                   
                 
                 ) 
               
             
             ≤ 
             α 
             ≤ 
             
               90 
               ⁢ 
               
                 ° 
                 . 
               
             
           
         
       
     
       FIG. 11  shows an exemplary embodiment of the construction of the contour of the recess  31  on the basis of a triangular section. In that case as well, the quantity “a” indicates the depth of the recess  31  in  FIG. 7 . The triangular cutout is characterized by the quantities “a” and “d” as well as recess angle α. The following applies for the relationship of those quantities relative to each other: 
     
       
         
           
             
               arctan 
               ⁡ 
               
                 ( 
                 
                   
                     2 
                     · 
                     a 
                   
                   d 
                 
                 ) 
               
             
             ≤ 
             α 
             ≤ 
             
               90 
               ⁢ 
               ° 
             
           
         
       
       
         
           wherein 
         
       
       
         
           
             
               0 
               ≤ 
               c 
               ≤ 
               d 
             
             ; 
             
               
                 a 
                 d 
               
               = 
               
                 1 
                 4.3 
               
             
             ; 
             
               0.1 
               ≤ 
               
                 a 
                 d 
               
               ≤ 
               1. 
             
           
         
       
     
       FIG. 12  shows various exemplary embodiments of configurations of the recess. The examples shown in  FIGS. 12   a  to  12   d  show various configurations of the recess in the form of combined, equivalent, or different radii R, whereas the exemplary embodiment shown in  FIG. 12   e  is a configuration of the recess  31  in the form of a portion of an ellipse.  FIG. 12   a  shows an exemplary embodiment of the recess  31  in the form of a portion of a circle having a radius R.  FIG. 12   b  shows an exemplary embodiment of the recess  31  in which two regions of the circular section identified by radius R are connected with each other by a straight segment  35 . In the exemplary embodiment shown in  FIG. 12   c , a concave radius RV in the region of the centerline  32  abuts a convex radius RX on both sides. The radii RV and RX are arranged in relation to each other so that there is a smooth transition between the individual radii and between the radii and the straight sections. Similar to the transition from exemplary embodiment  12   a  to exemplary embodiment  12   b , there is a straight section  35  in the area of the centerline  32  in the exemplary embodiment in  FIG. 12   d .  FIG. 12   e  shows an exemplary embodiment in which the recess  31  is in the form of a portion of an ellipse and hence has the shape of an elliptical portion. In  FIGS. 12   a  to  12   e , the baseline  33  is shown as a dot-dashed line and is only provided with a reference numeral in  FIG. 12   e  for the sake of clarity. 
     Although particular embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit of the present invention. It is therefore intended to encompass within the appended claims all such changes and modifications that fall within the scope of the present invention.