Abstract:
A chain including identically-configured plate elements having at least one through opening that overlaps with through openings of preceding and following plate elements. The plate elements are interconnected with identically-configured rocker members that extend into the plate openings. The rocker members are in the form of pins having an asymmetric cross-sectional shape that includes rolling surfaces and contact point surfaces that engage with the plate opening surfaces. Outer end faces of the rocker members are crowned to provide contact points that are asymmetrically positioned relative to a pin longitudinal central axis. By reversing the rocker member orientation within the plate element through openings, randomization of chain contacts with chain-driven components is achieved, with improved acoustics. And by utilizing identical plate elements and identical rocker members parts manufacture is simplified, as are part inventory requirements.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a chain, in particular a chain for a continuously variable belt-driven conical-pulley transmission, or a toothed chain. Areas of application for such chains are belt-driven conical-pulley transmissions, as well as toothed chains in general in machinery, for example as a pump drive or transfer chain for 4-wheel-drive power divider transmissions, or engine control chains.  
         [0003]     2. Description of the Related Art  
         [0004]     In a CVT transmission, i.e., a continuously variable belt-driven conical-pulley transmission, such chains are used to transmit the torque from the driving pulley to the driven pulley. As toothed chains, the chains made up of plate elements and rocker joints and have tooth geometries of the plate elements with which they engage with complementary tooth geometries and thereby also transmit forces or torques.  
         [0005]     Such chains made up of rocker joints and plate links usually contain two-piece rocker joints. The rocker joints are composed of two pin elements that extend through an opening in the plates, so that two pin elements extend through an opening of a plate element and of an adjacent plate element, and thus combine the plate elements into a chain. At the same time, they serve to ensure the movability of the chain links in relation to each other and to enable the transmission of power in the chain.  
         [0006]     It is known that when the chains are made up of identical plate elements the chain tends to develop increased noise during operation. An effort is therefore made to change the type of plates within the chain to improve the acoustics. For that purpose, it is known to construct chains having identical two-part rocker joints, but having different forms of plates. At the same time, those different plate types serve to prevent intersections. However, it is therefore necessary to keep the different plates separate during production and to install them selectively.  
         [0007]     Another alternative is to randomize the two-part rocker joints. For that purpose, the rocker joints are not made from two identical pins but from two different pins, for example a large pin and a small pin. Again, in that case two different parts must be processed separately during production and must be installed by a defined alternation pattern or by a random alternation pattern.  
         [0008]     An object of the invention is to provide an economical chain that has good acoustic properties and strength and is simple to produce.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is based on the concept of using only one pin, which has asymmetrical properties and hence results in different rolling behavior depending upon its direction of installation, and whose pressure transmission point, for example to a surface of a conical disk of a belt-driven conical-pulley transmission, changes within a plate element depending upon the installation position of the pin in the plate element.  
         [0010]     That means that depending upon the orientation of the pin serving as a rocker joint, of which preferably only a single element is provided per rocker joint, a different spacing is achieved between two adjacent pressure transmission points, or different rolling behavior of the pin in the particular plate openings bordering the pin, for example. For that purpose the pin is usable and insertable in at least two different installation positions in relation to a plate element.  
         [0011]     At the same time, it offers the possibility of henceforth using only one plate type instead of up to four, and needing only one pin, while the same randomization can be achieved as with up to four plate types and two pin elements per rocker joint. Thus a great advantage is achieved for the production technique from the fact that the number of parts is significantly reduced and the randomization of the chain structure can be accomplished with only two different elements, namely the pins and the plate elements.  
         [0012]     In accordance with a preferred embodiment of the invention, the pin element used as a rocker member is asymmetrical in terms of central symmetry and/or axial symmetry, wherein the relevant axis for axial symmetry is an axis perpendicular to the longitudinal direction of the chain in the extended state, so that the central axis of a pin element, that is, through the pin cross section perpendicular to the pin axis, can be defined as the line bisecting the maximum width of the rocker member in the longitudinal direction of the chain.  
         [0013]     Advantageously, the chain can be in the form of a toothed chain, so that the plate elements are toothed chain elements including a tooth geometry, preferably with two teeth on each plate element. At the same time, the teeth can also have a slightly varied tooth geometry to improve the acoustics of the chain. The purpose of that is so that when the chain is installed in one direction or the other, different meshing conditions of the teeth with the opposite parts are also achieved.  
         [0014]     In accordance with a preferred embodiment, the chain is used as a chain for a belt-driven conical-disk transmission (CVT transmission). Each pin preferably has an end face with an end face contact region for contact with surfaces of the conical disks of conical disk pair of the CVT transmission, for example, by which the transmission of force takes place. For example, the end faces can be designed as a convex surface, whose maximum projection is the eccentric end face contact point.  
         [0015]     Preferably, the plate elements are designed so that each plate element has only a single through opening, which overlaps both the through opening of the preceding plate element and the through opening of the subsequent plate element when the chain is assembled. Thus, two rocker joints can be provided by means of a single plate through opening.  
         [0016]     Preferably, each rocker member is made of only a single pin, so that each rocker joint has a pin and an associated plate contact region or rolling region.  
         [0017]     In accordance with a preferred embodiment, each pin is designed with two rolling surfaces, so that the contact surface of the pins is formed as a second rolling surface. The rolling surfaces can be centrally symmetrical or centrally asymmetrical relative to each other. With centrally asymmetrical rolling surfaces, the result is that different rolling behavior of the pins on the plate elements is achieved, in particular the contact surface region and the rolling surface region of the plate element, depending upon the installation position of the pin in the through opening of —the plate elements.  
         [0018]     Alternatively, the contact surface of the pin is designed as a non-rolling bearing surface, so that the pin, depending upon its installation position in the plate opening or plate bore, either meets an opposing rolling surface of the rolling surface of the pin at approximately the center of the height of the bore, for example, and is in rolling contact with the latter, or it bumps against an opposing contact surface, above and below the rolling surface, for example, if it is installed in the plate opening in the opposite orientation. The contact surface of the pin interacts with the opposing bearing surface, or opposing contact surface, and does not roll there. Instead, relative motion between the rocker member and the plate element is largely prevented in that installation position, if the contact surface of the rocker member and the contact surface region of the plate element are designed as bearing surfaces and are abutting against each other.  
         [0019]     Because of that arc-shaped or s-shaped pattern, for example, when designing the pin and the plate opening, it continues to be possible that despite the different functions that are integrated into the pin and the plate opening, the plate opening has a producible form, and in particular tight radii or sharp corners are avoided.  
         [0020]     Because of the fact that preferably each rocker member is made of only a single pin, the plate openings for the single pin can be made smaller than is the case when using two pins for each rocker joint. That makes it possible to shorten the plates, and thus to reduce the link pitch of the chain and thus the pitch of the pins. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     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:  
         [0022]      FIG. 1  is a fragmentary cross-sectional view of a first embodiment of a chain segment in accordance with the invention;  
         [0023]      FIG. 2  is a fragmentary cross-sectional view of a different pin installation position of a chain segment made up of the same elements as in  FIG. 1 ;  
         [0024]      FIG. 3  is a fragmentary cross-sectional view of an alternative embodiment of a chain segment in accordance with the invention;  
         [0025]      FIG. 4  is a perspective view of a rocker member in accordance with the invention;  
         [0026]      FIG. 4A  is a perspective view of an alternative version of a rocker member in accordance with the invention;  
         [0027]      FIG. 4B  is a cross-sectional view of the rocker member shown in  FIG. 4A ;  
         [0028]      FIG. 5  is a side view of a schematic representation of an embodiment of a chain in accordance with the invention;  
         [0029]      FIG. 6  is a side view of an alternative embodiment of a chain in accordance with the invention and in a schematic view;  
         [0030]      FIG. 7  is a fragmentary side view of a different alternative embodiment for a chain segment;  
         [0031]      FIGS. 7A and 7B  show side views of alternative embodiments of link plates;  
         [0032]      FIG. 8  is a side view of a chain arrangement in accordance with the invention for the chain segment shown in  FIG. 7 ; and  
         [0033]      FIG. 9A  is a graph showing the measured plate force during a chain revolution for a chain having two-piece rocker members, along with a side view of the physical arrangement; and  
         [0034]      FIG. 9B  is a graph showing the measured plate force in a chain revolution for a chain with a one-piece rocker member, along with a side view of the physical arrangement. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0035]      FIG. 1  shows a portion of a plate element  10  with a rocker member  20  in accordance with the invention. Rocker member  20  is shown in cross section in  FIG. 1 , and is designed as a pin whose longitudinal axis extends perpendicular to the drawing plane. One half of plate element  10  is shown in  FIG. 1 . The other half is symmetrical to the half that is shown, relative to the axis of symmetry S for a plate element  10 . Axis of symmetry S lies in a plane that is perpendicular to the plane of longitudinal extension of a chain when the chain is in the extended condition.  
         [0036]      FIG. 1  also shows schematically by lines  15 , which indicate the position of an opening of an adjacent plate element  10  on the left side, the positions of the second adjacent plate element on the left side in various movement conditions, and various rolling conditions of rocker member  20  relative to plate element  10 .  
         [0037]     Plate element  10  has a through opening  11 . Together with the left-side adjacent plate element  10  and its opening  11  and the right-side adjacent plate element  10  and its opening  11 , it is possible to insert two separate rocker members  20  into the one through opening  11 . Each rocker member forms a rocker joint with plate element  10 , and thus form two rocker joints to the preceding and the following plate elements  10 , respectively, with the adjacent wall regions of the through openings  11 .  
         [0038]     Through opening  11 , which is likewise of symmetrical design relative to the axis S, has a convex rolling surface region  12 , at a middle height in the direction of the plate element axis, arched toward the center of the plate element, and above and below it adjacent contact surface regions  13  that are formed as concavely curved regions. As can be seen schematically from the line shape of the outlines of adjacent plate element  10  (lines  15 ), adjacent plate element  10  is of identical design and also has concavely curved contact regions  13  and a convexly curved rolling surface region  12  lying between the concavely curved regions  13 , as boundaries of the contour of the opening.  
         [0039]     Rocker member  20  is of central point asymmetrical design with regard to its cross section. In particular, it has (on the left side in  FIG. 1 ) two convexly curved contact surfaces  23 , and on the opposite side a rolling surface  22 . Preferably rocker member  20 , in the form of a pin, is provided with identical cross sections along its longitudinal axis, except for the region of the end face (see  FIG. 4 ).  
         [0040]     In  FIG. 1  rocker member  20  is inserted into the through opening  11  of the plate element in such a way that the convex contact surfaces  23  of rocker member  20  are in contact with the contact surface regions  13  of plate element  10 , and hence do not roll on it but are largely fixed relative to it. A second rocker member  20  (not shown) that is guided by the plate element  10  shown in  FIG. 1 , can either be inserted in mirror image symmetry relative to axis S, or it can be in the same orientation as the rocker member  20  that is shown for the left half of plate element  10  in  FIG. 1 . The various installation options produce randomization.  
         [0041]      FIG. 2  shows the situation in which a pin that is identical to rocker member  20  is inserted into a plate element identical to that in  FIG. 1 , likewise in its left half, but with the orientation of the pin rotated. In contrast to  FIG. 1 , in which the right side plate (shown) is firmly abutting against rocker member  20  because of the installation orientation of rocker member  20 , and the left side plate (shown by lines  15 ) rolls on the pin or rocker member  20 , in the mirror image installation of  FIG. 2  the left plate element  10  rolls on rocker member  20 , since the rolling surface region  12  of through opening  11  and the rolling surface  22  of rocker member  20  roll on each other. The right plate (shown by lines  15 ) abuts firmly on rocker member  20  and does not roll. The contact surface regions  13  of through opening  11  of the right plate  10  shown in  FIG. 2  have no function.  
         [0042]     Hence, with the same geometric design of the plate elements  10  and the rocker members  20 , because of the mirror image installation of the rocker member  20  in a particular plate element the functions of the individual edge regions of the through opening  11  of the plate element are utilized differently. As a result, by changing the function and through random installation of the rocker members  20  in the one direction or the other, randomization of the functions can be achieved.  
         [0043]      FIG. 3  shows an embodiment of plate element  10  in which two separate through openings  11  or plate throughbores are provided for the rocker joint region to the left-hand adjacent plate element and the rocker joint region to the right-hand adjacent plate element. The design of the functional surfaces that form the contour of the through opening  11 , as contact surface regions  13  and rolling surface region  12  between the contact surface regions  13 , is identical to the embodiment shown in  FIGS. 1 and 2 . The pin geometry of the rocker member  20  is likewise identical.  FIG. 3  shows the situation in which a rolling contact is established between the rolling surface  22  of rocker member  20  and the rolling surface region  12  of plate element  10 . With the adjacent plate element  10  on the left (not shown), which has a geometry identical to that of the illustrated plate element  10 , the contact region  23  of rocker member  20  enters into a non-rolling contact with the contact surface  13  of plate element  10 .  
         [0044]      FIG. 4  shows a perspective view of the rocker member  20  for the arrangement shown in  FIGS. 1 through 3 . Along the longitudinal axis L of the pin, the rocker member  20  has the identical cross-sectional contour, which is recognizable in cross section in  FIGS. 1 through 3  and has already been described.  
         [0045]     The end faces  24  of rocker member  20  are designed as convex end faces, preferably with a crowning  25  or convexity provided in two directions perpendicular to each other, so that a furthest protruding point results that is the end face contact point  26 . Because of the particular design of the crowning  25 , the end face contact point  26  is preferably situated asymmetrically relative to a center axis of the pin element, which center axis is perpendicular to the longitudinal axis L of the pin and parallel to the axis of symmetry S of the plate element  10 , i.e., perpendicular to the chain extension direction when the chain  30  is extended longitudinally. End face contact point  26  is preferably not positioned on that axis, which produces its asymmetry on the end face  24 . End face contact point  26  is that point with which the rocker joints  20  come into pressure contact with the conical disks of a belt-driven conical-pulley transmission, for example.  
         [0046]      FIGS. 4A and 4B  show an alternative embodiment of a rocker member  20   a  in which concave rolling surface region  22  of pin  20  shown in  FIG. 1  is replaced by flat surface region  22   a.    
         [0047]      FIG. 5  shows a schematic side view of a portion of a chain  30  that utilizes the chain elements shown in  FIGS. 1 through 4 . In particular, the plate elements  10  are shown schematically in  FIG. 5 . As can be seen from  FIG. 5 , the rocker members  20  are installed randomly in the positions shown in  FIG. 1  or in  FIG. 2 . That results in a random distribution of the spacings B between each pair of adjacent end face contact points  26 , and a random distribution of the pitch spacings A between adjacent rocker joints  32 . In particular, if two pins are installed in a plate element  10  one after the other in the same orientation, such as the first two pins starting from the left in  FIG. 5 , the result is both medium rolling surface spacings A and medium end face contact point spacings B. If the left rocker member is installed in a plate element in the orientation of  FIG. 1  and the rocker member to its right is installed in mirror image symmetry to it, as in the case of the third and fourth rocker members  20 , as viewed from the left in  FIG. 5 , the result is short spacings B of the end face contact points  26  and short rolling spacings A. Finally, if the left rocker member in a plate element  10  is installed in the installation position of  FIG. 2  and the right rocker member is installed in mirror image symmetry to it, as in the case of rocker members  5  and  6 , As viewed from the left in  FIG. 5 , it produces a long spacing B between the end face contact points  26  and a long rolling spacing B. Thus, it is possible to achieve three different rolling spacings A and three different contact point spacings B of the end face contact points  26  while using only one form of plate element  10  and one form of rocker member  20 , which also alternate in a random sequence along the chain  30  when the arrangement of the rocker members  20  is randomized.  
         [0048]      FIG. 6  shows the use of the geometry for plate elements  10  and rocker members  20  in accordance with the invention for toothed plate elements. As can be seen from  FIG. 6 , each plate element  10  has two schematically shown teeth  27 ,  27   a . The tooth geometries can likewise differ from each other in accordance with need and thus contribute to randomization of the tooth engagement, depending upon the installation direction of the plate elements  10 . The configuration of the end faces of the rocker members  20  is not significant in that case. The figure shows the randomization of the rolling spacings A. The cross-sectional geometry of the rocker members  20  and of the through openings  11  of the plate elements is as shown in  FIGS. 1 through 3 .  
         [0049]      FIG. 7  shows an alternative embodiment for the geometry of the through openings  11  of the plate elements  10  and of rocker members  20 . An end face contact point  26  is again provided asymmetrically on the ends of each rocker member  20 . The plate elements  10  are symmetrically structured relative to the axis of symmetry S.  
         [0050]     In contrast to the plate elements  10  and rocker members  20  described in connection with  FIGS. 1 through 6 , each rocker member  20  of  FIG. 7  has two rolling surfaces  22 , i.e., the contact surface  23  shown in  FIG. 1  is designed as a second rolling surface  22 . The rolling surfaces are provided on sides lying opposite each other relative to a central axis through rocker member  20  that is parallel to the axis S of the plate elements when the chain is extended longitudinally. The end face contact point  26  lies outside the axis; that is, it is asymmetrically positioned on the end of rocker member  20 . The rolling surfaces  22  are preferably of different form, in particular if the noise reduction of the chain  30  is to be achieved by randomizing both the spacings B of the end face contact points  26  and the rolling spacings A. The through openings  11  of the plate elements  10 , of which each plate element  10  has two, also have two oppositely positioned rolling surface regions  12 . Instead of designing the pin geometries differently with respect to each other in regard to the rolling surface regions  12 , the two rolling surface regions  12  of a through opening  11  of the plate element  10  can also have different geometries. That means that in the embodiment shown in  FIG. 7 a  contact surface region  13  of the plate element  10  is designed as a rolling surface region  12 , and a contact surface of the rocker member  20 , in the form of a pin, is likewise designed as a rolling surface  22 .  
         [0051]      FIGS. 7A and 7B  show differently configured plate elements  10 A and  10 B, respectively. As can be seen, the through openings  11 A and  11 B differ in their overall configuration, while the rocker members  20  are of the same cross-sectional form.  
         [0052]     With the end face contact points  26  positioned eccentrically on the ends of rocker members  20 , and with the rocker members aligned at random in the plate through openings  11  within a chain such as chain  30  of  FIG. 5 , it is again possible, as shown in  FIG. 8 , to achieve different spacings B of the end face contact points  26 . If either the through openings  11  of the plate elements  10  or the cross sections of the rocker members  20  are of asymmetrical design in terms of central point symmetry, then a randomizing of the rolling spacings (not shown in  FIG. 8 ) is also possible.  
         [0053]     In each of the illustrated embodiments, the randomization is made possible with a single configuration of the plate elements  10  and a single configuration of the rocker members  20 .  
         [0054]     The advantages of utilizing a one-piece rocker member  20 , with which a rocker joint  32  can be formed from a single rocker member  20  and the corresponding plate opening  11 , are illustrated in  FIGS. 9A and 9B  in comparison to two-piece rocker members. The graph in  FIG. 9A  shows the measured total longitudinal force acting on a plate element during one chain revolution for a two-piece rocker joint  32 , while the graph in  FIG. 9B  shows the measured total longitudinal force acting on a plate element for a one-piece rocker joint  32 .  FIGS. 9A and 9B  register, respectively, the sums of the upper forces F o  and the lower forces F u  acting at the regions of the plate elements  10  a shown at the right sides of  FIGS. 9A and 9B . It can be seen that damaging force peaks in the plates can be moderated through the use of only one pin as the rocker member  20 , and thus the changed rolling kinematics that accompany the force peaks can be reduced. That contributes to the reliability and durability of the chain. In addition, because of the small number of parts needed, a production advantage can be achieved, as is necessary in particular for small businesses and in the case of toothed chains.  
         [0055]     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.