Abstract:
A plate-link chain having a plurality of link plates hingedly connected with each other by pairs of rocker members that each include two rocker members. The rocker members extend transversely to the longitudinal direction of the plate-link chain and are situated with play in openings in the link plates. The rocker members and the link plate openings each have respective curved contact surfaces along which the rocker members and the link plates bear against each other to transmit force. The rocker members include curved rolling surfaces along which the rocker members roll against each other during chain operation to transmit force. The play value between the rocker members and the opening in an adjacent link plate is less than 0.2 mm to minimize lateral vibrations of the chain during operation, to prevent contact of the chain with an enclosing housing and thereby reduce emitted noise.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a plate-link chain having a plurality of link plates that are hingedly connected with each other by pairs of rocker members. 
         [0003]    2. Description of the Related Art 
         [0004]    Plate-link chains generally include rocker member pairs that are composed of two rocker members each, wherein the rocker members extend transversely to the longitudinal direction of the plate-link chain. The rocker member pairs are positioned within openings in the link plates and with some degree of play therebetween. Curved contact surfaces are provided on the rocker members and on the link plates, along which curved surfaces the rocker members and link plates bear against each other to transmit force. The rocker members include curved rolling surfaces along which the rocker members of a rocker member pair roll against each other and/or slide on each other to transmit force. 
         [0005]    Such a plate-link chain can be used as a means of transmitting traction force in a belt-driven conical-pulley transmission, or as a toothed plate-link chain in a toothed belt-driven transmission, in motor vehicles or the like, for example. In a plate-link chain the tractive force is transferred by means of frictional contact between outer ends of the rocker members and the conical disk surfaces of the two conical pulleys. In the case of a toothed plate-link chain the tractive force is transferred through meshing of the teeth of the toothed plate-link chain with teeth of the toothed wheels. 
         [0006]    In the region of the plate-link chain or toothed plate-link chain that is not encircling the conical pulleys or toothed wheels, i.e., in the region in which the plate-link chain is running freely, the chain can vibrate laterally. That involves transverse vibrations of the chain in the direction of the axes of rotation of the conical pulleys or toothed wheels. Furthermore, vibrations of the plate-link chain or toothed plate-link chain are possible in the direction of force transfer and again perpendicular to the direction of force transfer as so-called strand vibrations. 
         [0007]    In particular, lateral vibrations of the plate-link chain or toothed plate-link chain increase the necessary structural space for the housing of a transmission, because striking of the chain against the housing wall should be avoided. 
         [0008]    An object of the present invention is therefore to provide a plate-link chain or a toothed plate-link chain that has a small vibration amplitude, in particular in the case of lateral vibrations. In addition, the invention relates to the use of such a plate-link chain in a belt-driven transmission. 
       SUMMARY OF THE INVENTION 
       [0009]    The object is achieved by a plate-link chain having a plurality of link plates hingedly connected with each other by pairs of rocker members that include two rocker members each. The rocker members extend transversely to the longitudinal direction of the plate-link chain and are positioned with some degree of play in openings in the link plates. Curved contact surfaces are provided on the rocker members and on the link plates, along which curved surfaces the rocker members and link plates bear against each other to transmit force. The rocker members include curved rolling surfaces along which the rocker members roll against each other and/or slide on each other to transmit force. 
         [0010]    The play between the rocker members and the opening in an adjacent link plate is less than 0.2 mm. A play of from about 0.05 mm to about 0.15 mm has proven to be especially advantageous. As hereafter used herein, the term plate-link chain includes a toothed plate-link chain. In addition, it has proven to be especially advantageous if the link plates have a thickness in a direction transverse to the longitudinal direction of the plate-link chain, and that the play is one fiftieth ( 1/50) to one fifteenth ( 1/15) of the thickness of the link plate. It has been found that due to the play of from about 0.05 mm to about 0.15 mm, or with a play S that is approximately one fiftieth ( 1/50) to one fifteenth ( 1/15) of the thickness of the link plates, a distinct reduction of the tendency of the plate-link chain to vibrate laterally results. 
         [0011]    A refinement of the plate-link chain in accordance with the invention provides that the openings have play reduction points that limit the play locally to from about 0.05 mm to about 0.15 mm, and/or to one fiftieth ( 1/50) to one fifteenth ( 1/15) of the thickness of the link plates. Instead of limiting the play across the entire contour of the openings or rocker members, the desired effect can be achieved through individual selected locations at which there is less play. 
         [0012]    In a further preferred embodiment of the plate-link chain in accordance with the present invention there is provided a perpendicularity tolerance of the inner surface of the openings that is smaller than 0.02 mm. In another preferred embodiment of the plate-link chain in accordance with the present invention, it is provided that the openings have at least three regions that are curved convexly inward. The convexly-inwardly-curved regions limit the ability of the rocker members to twist relative to the link plates. Preferably, the rocker members are asymmetrically formed in a cross section running in the longitudinal direction of the plate-link chain in the direction of the rocker member height. The asymmetrical design results in a more favorable introduction of the pressure forces in the region of the contact surfaces between the rocker members and the link plates. 
         [0013]    The object identified earlier is also achieved by the use of a plate-link chain in accordance with the invention in a belt-driven transmission, in particular as a plate-link chain in a belt-driven conical-pulley transmission with a continuously variable transmission ratio, or as a toothed plate-link chain in a toothed wheel transmission. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    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: 
           [0015]      FIG. 1  is a side view of a toothed plate in accordance with the existing art; 
           [0016]      FIG. 2  is a portion of a further tooth plate in accordance with the existing art; 
           [0017]      FIG. 3   a  is an illustration of the play of a rocker member pair in openings of the link plates of a toothed plate-link chain in accordance with the existing art; 
           [0018]      FIG. 3   b  is an illustration of the play of a rocker member pair in openings of the link plates of a toothed plate-link chain in accordance with an embodiment of the present invention; 
           [0019]      FIG. 4  is a longitudinal cross section through a plate-link chain in accordance with the present invention in a top view; 
           [0020]      FIG. 5  is a section through a plate-link chain in accordance with the invention corresponding to the view of the plate-link chain in  FIG. 4 ; 
           [0021]      FIG. 6  is an enlarged, fragmentary top view of a link plate of  FIG. 5 ; 
           [0022]      FIG. 7  is a schematic top view of a belt-driven transmission having a toothed plate-link chain in accordance with the present invention or a toothed plate-link chain in accordance with the existing art to illustrate the lateral vibrations of the chain. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]      FIG. 1  shows link plates  1  and  1 ′, which are designed as toothed plates, as a detail of a toothed plate-link chain  22  that is otherwise not shown. In the case of a toothed plate-link chain the link plates  1  and  1 ′ are provided with two teeth  2  and  2 ′; in a plate-link chain the teeth  2  and  2 ′ are omitted. Plate-link chain  22  is formed in a known manner by the alternating overlapping arrangement of link plates  1  and  1 ′, whereby the link plates  1 ,  1 ′ forming part of adjacent chain links are hingedly connected to each other by rocker member pairs  3 . The rocker member pairs  3  each include a first rocker member  4  and a second rocker member  4 ′, which roll against each other on respective rolling surfaces  23  when plate-link chain  22  bends as it around a pulley. Each rocker member pair  3  is received in a receiving opening  7  of link plate  1 ; the receiving opening  7  includes a contact surface  6 . 
         [0024]    In the representation in  FIG. 1 , rocker member  4  bears against the contact surface  6  of link plate  1 , while rocker member  4 ′ bears against the contact surface  6 ′ of the adjacent link plate  1 ′. Rocker member  4  has a curved contact surface that bears against the contact surface  6  of receiving opening  7  of link plate  1 . Rocker member  4 ′ has a corresponding curved contact surface  5 ′ that bears against the contact surface  6 ′ of a receiving opening in link plate  1 ′, which is laterally adjacent to link plate  1 . The surface  8  of receiving opening  7  located opposite the contact surface  6  is designed so that a gap  24  is formed between the curved surface  5 ′ of rocker member  4 ′, which bears against a receiving opening in the adjacent link plate  1 ′, and surface  8  of receiving opening  7 . Thus, rocker member  4 ′ does not touch the surface  8  of receiving opening  7  of link plate  1 . A corresponding gap also exists between rocker member  4  and the surface of a corresponding receiving opening in link plate  1 ′. 
         [0025]      FIG. 2  shows a detail of a further known link plate  1 . The adjacent link plate  1 ′ is not shown, and only the left part of the link plate  1  corresponding to the representation in  FIG. 1 , and associated with tooth  2 , is shown. Receiving opening  8 ′ has three convexly curved lobes A, B, and C that extend inwardly into receiving opening  8 ′. Rocker member  4  of rocker member pair  3  has a concave contraction AW which is associated with and is opposite to lobe A, while rocker member  4 ′ has a contraction BW that is associated with and is opposite to lobe B. Contraction AW bears against lobe A when the chain bends. Correspondingly, the contraction BW of rocker member  4 ′ bears against lobe B when the plate-link chain bends, and thus excessive twisting of the rocker members  4  and  4 ′ against each other is prevented, in particular if the plate-link chain swings back. 
         [0026]    The lobe C, situated toward the upper surface of the chain, when viewed in the running direction, serves to secure the rocker members  4  and  4 ′ against twisting when the plate-link chain bends. A dashed circle  9  in  FIGS. 1 and 2  clearly shows a region with a relatively large spacing between the surface of rocker member  4 ′ and the surface of receiving opening  8 ′ of link plate  1 . In the embodiment of the plate-link chain in accordance with  FIG. 2 , possible motion in the direction of double headed arrow R of the rocker member  4 ′ relative to rocker member  4  is determined by the distance ax between the surface of rocker member  4 ′ and the surface of receiving opening  8 ′ of link plate  1 . 
         [0027]      FIG. 3   a  shows a side view of two known link plates  1  and  1 ′ corresponding to the representation in  FIG. 1 , to clearly show the play between the rocker members and the two link plates  1  and  1 ′. A play value designated as S between the rocker members and the link plates  1  and  1 ′ is caused by the loose reception of the rocker member pair  3  in the receiving opening  7  of link plate  1  and the receiving opening  7 ′ of link plate  1 ′. Link plate  1 , as well as the receiving opening  7  of link plate  1  and the rocker member  4  supported in receiving opening  7 , are shown in dashed lines in  FIG. 3   a . Link plate  1 ′, the associated receiving opening  7 ′ and the rocker member  4 ′ supported in the receiving opening are shown with solid lines. The link plates  1  and  1 ′ have a play value S relative to the rocker member pairs  3 . The two link plates  1  and  1 ′ can thus be moved relative to each other by the play value  2 S. For a known plate-link chain the play is about 0.2 mm, so that the total play within the entire length of the known plate-link chain adds up to several millimeters. 
         [0028]      FIG. 3   b  shows two link plates  1  and  1 ′ of a plate-link chain  22  in accordance with the present invention, wherein the play value S is reduced to a value of from about 0.05 mm to 0.15 mm. The reduction of the play from 0.2 mm in the known chains to a value of between 0.05 mm to 0.15 mm can occur locally at one place, for example at a local play reduction point  10  or  10 ′ as shown in  FIG. 3   b . The local play reduction points  10  and  10 ′ are preferably situated so that they cause the play reduction only when the plate-link chain is not bent, so that in the bent state the play reduction points nevertheless do not come into contact with the rocker members  4  or  4 ′.  FIG. 3   b  shows the play reduction for a toothed plate-link chain corresponding to the representation of the link plate in  FIG. 2 , i.e., a toothed plate-link chain in which the individual chain links are provided with lobes A, B, and C. However, the play value reduction to S=0.05 mm to 0.15 mm can also be made with a plate-link chain in accordance with  FIG. 1 , i.e., a plate-link chain without lobes. 
         [0029]    The reduction of the play value S by local play reduction points  10  and  10 ′ is accomplished in that the receiving openings  7  and  7 ′ have a zone in the region of the opening surfaces  8  or  8 ′ that reduces the play to a value of S=0.05 to 0.15 mm, in particular when the plate-link chain is not bent. In that case the play S is about one fiftieth ( 1/50) to one fifteenth ( 1/15) of the thickness b of link plate  1 . The thickness b of link plate  1  is shown in  FIGS. 4 and 5  and is the thickness of the link plates measured in the transverse direction in a top view of the plate-link chain. 
         [0030]    It has been found that because of the reduced play to a value of 0.05 mm to 0.15 mm, or with a play-value S that is approximately one fiftieth ( 1/50) to one fifteenth ( 1/15) of the thickness of the link plates, a distinct reduction of the tendency of the plate-link chain to vibrate laterally results, which vibratory mode is shown in  FIG. 7 . 
         [0031]      FIGS. 4 and 5  each show fragmentary longitudinal cross-sections through a plate-link chain in accordance with the invention in top views. The figures show stacks of portions of link plates of two adjacent chain links corresponding to the representation in  FIGS. 3   a  and  3   b , with one link plate  1  and two link plates  1 ′ of two adjacent chain links shown. Because of the play value S represented in  FIGS. 3   a  and  3   b , rocker members  4  and  4 ′ are able to carry undergo a tilting motion in the longitudinal direction of the plate-link chain. As shown in  FIG. 4 , the longitudinal axis  11  of the rocker member pair  3 , or of rocker members  4  and  4 ′, then deviates from the transverse axis  12  of the plate-link chain by a tilt angle α. Transverse axis  12  is perpendicular to the chain running direction, which is shown in  FIG. 4  by double headed arrow  13 . The reduction of the play value S in accordance with the present invention causes the tilt angle α to be reduced, as shown in  FIG. 5 . 
         [0032]    An additional reduction of the play value S and of the tilt angle α is achieved by the perpendicularity tolerance of the inner surfaces of the receiving openings  7  and  7 ′ of the link plates  1  having a value smaller than 0.02 mm. To illustrate the perpendicularity tolerance R, a reference surface  14  and an arrow  15  are shown in  FIG. 6 . In that respect the illustrated representation corresponds to DIN ISO 1101. A tolerance axis  16  of the receiving opening  7  or  7 ′ of a link plate  1  or  1 ′ must be spaced at a distance less than 0.02 mm between two parallel planes  17  and  17 ′, which are perpendicular to reference surface  14  and to the direction of arrow  15 . For clarification this is shown in  FIG. 6  in enlarged form on the basis of the chain link  1 ′ shown in  FIG. 5 . The distances R1 and R2 from tolerance axis  16  to reference planes  17  and  17 ′ are both smaller than 0.02. The distances R1 and R2 from axis  16  to reference surfaces  17  and  17 ′ add up to the perpendicularity tolerance R, where R1&lt;R and R2&lt;R. 
         [0033]      FIG. 7  illustrates the effect of the play reduction in accordance with the present invention, and of the reduction of the perpendicularity tolerance R in accordance with the present invention.  FIG. 7  shows a schematic top view of a belt-driven transmission including a first toothed wheel  18  and a second toothed wheel  19 , each of which is encircled by a toothed plate-link chain  20 . When the belt-driven transmission is in operation the plate-link chain  20  can execute lateral vibrations, the directions of which are identified by double headed arrow  21 . The lines representing the maximum excursion of chain  20  are shown as dashed lines for a known toothed plate-link chain  20 , and as solid lines for a toothed plate-link chain in accordance with the present invention. The tendency to vibrate laterally, i.e., the excursions in the directions indicated by the double headed arrow  21 , is reduced significantly by the design of the plate-link chain or toothed plate-link chain in accordance with the present invention. As a result, the plate-link chain in accordance with the present invention does not strike against a housing wall of the belt-driven transmission, so that acoustic emissions resulting from the lateral vibration of the are reduced. 
         [0034]    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.