Abstract:
A traction engine drive ( 2 ), the components of which are integrated into an assembly unit ( 6 ) that can be pre-completed. A guide rail ( 7 ) having a clamp rail ( 10 ) is fixed in location by a clamping device ( 16 ) and a traction element ( 12 ) is disposed in conjunction with at least one traction mechanism wheel, so that a free length of the traction element is not present.

Description:
BACKGROUND 
     The present invention relates to a mounting unit of a traction element drive that is constructed, in particular, as a chain drive that can be used in internal combustion engines. The traction element drive comprises a drive wheel and at least one driven wheel that are connected by a traction element, wherein a guide rail or a tensioning rail connected to a tensioning system is allocated to each section of the traction element. 
     From DE 39 09 458 A1, a mounting unit for a traction element drive is known that comprises a chain wheel holder as well as a chain guide element for the timing chain of an internal combustion engine. This mounting unit includes arc-shaped holders in which the chain wheels and the timing chain are loosely placed. A tensioning device allocated to the traction element drive is supported on the chain on the outside with a non-positive fit. Because the tensioning device is mounted biased in connection with the traction element drive, the mounting complexity increases, because, for example, influenced by the effect of the tensioning device, it is difficult to mount the chain wheels onto the associated shaft ends. 
     EP 0 848 139 A1 relates to a mounting unit in which the traction element wheels are inserted into holding pockets and are positioned by the traction element wrapping around these wheels and are fixed by a catch element of the holding device. The mounting unit includes an arc-shaped tensioning rail which is pressed upon, in the operating state, by a chain tensioner positioned on the engine block of the internal combustion engine. For the mounting, the tensioning rail is held by a catch element in a home position that generates a certain amount of biasing in the traction element. 
     In common, the mounting units described above are left in place after completion of the mounting on the internal combustion engine. With respect to the relatively high number of pieces in internal combustion engines and the decreasing cycle times due to advancing automation in the automotive industry, the mounting units in the individual components and functions are subject to a constant demand for improvement and adaptation to rising requirements. 
     SUMMARY 
     The present invention is based on the objective of providing a mounting unit for traction element drives whose components are positioned captively secured in a preassembled state optimally without a separate component. 
     This objective is met according to the invention by a mounting unit that comprises components leading or biasing the traction element, as well as the traction element of the traction element drive. Advantageously, the components forming a module are shaped and assembled so that these require no separate components, such as, e.g., a carrier element, in order to allow a secure mounting of the traction element drive in or on the internal combustion engine. According to the invention, the pivoting tensioning rail is connected on the end via a pivot to the guide rail that is fixed in position in the operating state and that has a one-part or multiple-part construction. For creating an effective and durable transport securing device, the tensioning rail is preferably fixed indirectly or directly by a clip connection to the guide rail. Furthermore, the mounting unit includes a holding segment by which at least one traction element wheel is held in the preassembled state and for simplified mounting. 
     Advantageously, the mounting unit according to the invention offers a fixed transport position for the guide rail and the tensioning rail, as well as at least one traction element wheel, wherein, in contrast to previous mounting units, a disadvantageous free traction element length without additional components is eliminated. The construction according to the invention further allows a large percentage of equivalent parts, so that the mounting unit can be used for different internal combustion engines by supplementing and/or replacing a few individual components. 
     Additional advantageous constructions are described below. 
     A preferred construction of the invention provides a pivot containing a rotational lock between the tensioning rail and the guide rail. This pivot known for example, from pipe or water-pump wrenches comprises a locally flattened cylindrical pin that is connected to the pivoting tensioning rail or the guide rail. The pin engages in two circular-ring-shaped contours of the associated additional component shaped to a large extent like an 8 and enclosing holders connected by a web. By pivoting the tensioning rail into an extreme position facing away from the operating position, there is the ability to move the pin into the contours, i.e., between the holders, because a pin dimension in the region of a flattened section is less than a width of the web. This pivot construction guarantees the use of tensioning and guide rails with equal dimensions for different internal combustion engines or for traction element drives with traction element layouts deviating from each other. Advantageously, in connection with these conditions, the component scope of a motor vehicle manufacturer can be reduced. 
     Preferably, the guide rail is provided integrally with a leg or a lever that is provided on the end with a component forming the pivot, the pin or the contours shaped like an 8 for the pivot. In the installed state, the pivot element of the guide rail engages with a positive fit in the associated, additional pivot element of the tensioning rail. As an alternative, it presents itself to provide the tensioning rail integrally with a leg or lever that encloses a pivot element on the end side. 
     As the transport securing device and simultaneously as the captive securing device in the preassembled state of the traction element drive, according to the invention a positive-fit and/or non-positive-fit clip connection is provided. A holder bounded by elastic brackets is preferably suitable for this purpose, wherein these brackets enclose catch tabs or projections that are directed toward each other and on which the tensioning rail engages. The brackets are arranged directly on the guide rail or on an additional component allocated to the guide rail. 
     For traction element drives with several driven wheels, for example, the timing drive including two camshafts in an internal combustion engine, it presents itself according to the invention to combine the stationary guide rail with an additional guide rail component. This measure allows the traction element to be guided in the tensioned section in the region between the timing wheels. In this way it is guaranteed that, in all of the section regions of the traction element, a guide rail or tensioning rail is allocated to the traction element. Advantageously, the two guide rails assembled into a unit are mounted permanently by a non-positive-fit and/or positive-fit connection. Sleeves that are allocated, for example, to a guide rail are suitable for this purpose, wherein these sleeves are fit with a positive-fit connection in corresponding holders of the additional guide rail and are secured by a clip connection. 
     An additional advantageous construction of the invention relates to an anti-jumping device for the traction element in the region of the traction element wheels. For this purpose, each guide rail has on the end a tongue-like projection that is adapted to the shape of the traction element wheels and that is set apart from the outer contours of the traction element in the radial direction and that effectively stops the traction element from jumping. This construction likewise presents itself for a multiple-part guide rail, in order to obtain an anti-jumping device in the region of all of the driven wheels of the traction element drive. 
     The mounting unit constructed as a module can be further expanded by a holding segment with which a traction element wheel can be positioned in a preassembled way. For holding the drive wheel in the mounting unit it presents itself to allocate the holding segment to the guide rail directly or to the leg of the guide rail. As an extension of this configuration, the invention includes additional holding segments, in order to hold all of the drive wheels and driven wheels of the traction element drive in the mounting unit. 
     As a suitable material for the tensioning rail and the guide rails, plastic, in particular, PA66/H is provided. As an alternative, additional plastics are suitable that satisfy all of the requirements for the use of the traction element drive with respect to wear and strength. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will be explained below in detail with reference to drawings. Shown are: 
         FIG. 1  the traction element drive of an internal combustion engine, whose individual parts form a mounting unit, 
         FIG. 2  the traction element drive detached from the internal combustion engine in the operating state, 
         FIG. 3  a view of the individual part tensioning rail, 
         FIG. 4  a view of the individual part guide rail of the traction element drive, 
         FIG. 5  an enlarged view of a cutout of the tensioning rail according to  FIG. 3 , 
         FIG. 6  a view of an individual part sub-rail allocated to the guide rail. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a portion of an internal combustion engine  1  and here illustrates a traction element drive  2  constructed as a timing drive in the preassembled state, wherein this drive is designed for driving two camshafts  3   a ,  3   b , with driven wheels  5   a ,  5   b  drawn with dashed-dotted lines being allocated to each of these camshafts, respectively, in the operating state. The mounting unit  6  constructed as a module is limited exclusively to the components of the traction element drive  2 . The mounting unit  6  comprises a guide rail  7  that is stationary in the operating state and that is made from a base rail  8  with an associated sub-rail  9 . The mounting unit  6  further includes a pivoting tensioning rail  10 , the drive wheel  4  positioned by a holding segment  11 , as well as traction element  12  wrapping around the drive wheel  4  and guided further on the rails. In the delivery state of the mounting unit  6 , the tensioning rail  10  is fixed in position on the sub-rail  9  by a transport securing device  13 . As the transport securing device  13 , a clip connection shown in  FIG. 5  is provided that has two projecting, elastic brackets  14   a ,  14   b  set apart in the axial direction with local projections  15   a ,  15   b  that are directed toward each other and on which the tensioning rail  10  locks in the transport position. The construction of the mounting unit  6  causes a certain biasing of the traction element  12  in the transport position, wherein a disadvantageous free length of the traction element  12  is eliminated, which advantageously allows an unimpaired transport of the mounting unit  6  including all of the components of the traction element drive  2 . As a deviation from the diagram according to  FIG. 1 , it presents itself that the mounting unit  6  also includes the driven wheels  5   a ,  5   b  that are drawn with dashed-dotted lines and that are guided securely in the mounting unit  6  likewise wrapped around by the traction element  12 . In order to guarantee the changed traction-means guidance required here, a modified transport securing device  13  can be used accordingly in which the tensioning rail  10  partially pivoted in the counterclockwise direction is fixed in a position deviating from that in  FIG. 1 . In the operating state, the tensioning rail  10  is pivoted until it contacts the tensioning device  16  positioned stationary in the internal combustion engine  1 , by which a sufficient biasing of the traction element  12  is always guaranteed. 
       FIG. 2  shows additional details of the traction element drive  2  forming a mounting unit  6 . In a first tensioned section  17  set between the drive wheel  4  and the driven wheel  5   b , the base rail  8  of the guide rail  7  is supported on the traction element drive  2  rotating in the clockwise direction. The sub-rail  9  is allocated on the inside to the traction element  12  to the additional tensioned section  18  set between the driven wheels  5   a ,  5   b . The tensioning rail  10  that can pivot via a pivot  19  is supported on the traction element  12  on the outside in a slack section  20 , wherein the supporting force is triggered by the tensioning device  16 . The pivot  19  is formed by the leg  21  mounted integrally on the base rail  8  as well as the tensioning rail  10 . The leg  21  further includes the holding segment  11  by which a position of the drive wheel  4  in the transport position of the mounting unit ( 6 ) is guaranteed. The construction of the guide rail  7  provides that the sub-rail  9  to a large extent filling up the intermediate space set between the driven wheels  5   a ,  5   b  is connected preferably by a positive-fit and/or non-positive-fit attachment  22  to the base rail  8 . In common, both the base rail  8  and also the sub-rail  9  include a tongue-like anti-jumping device  23 ,  24  that extends in the direction of the associated driven wheel  5   a ,  5   b  and stops a disadvantageous lifting of the traction element  12  from the driven wheels  5   a ,  5   b . The tensioning device  16  has a vent  25  on the tensioning-rail side via which air enclosed in the tensioning device  16  in the operating state of the traction element drive  2  can escape unimpaired. Furthermore, the vent  25  allows a dosed discharge of the hydraulic fluid that can be used for lubricating the traction element  12 . For this purpose, a jet  26  coming from the vent  25  is led selectively through an opening  27  of the tensioning rail  10  onto the traction element  12 . 
       FIGS. 3 and 4  each show the tensioning rail  10  and the base rail  8  of the guide rail  7  in a individual-part views. The base rail  8  forms a contact  28  that is a component of the attachment  22  for the sub-rail  9  offset to the anti-jumping device  23 . On the end facing away from the anti-jumping device  23 , the base rail  8  comprises a projecting leg  21  that has, on the free end, contours  30  that are essentially shaped like an 8 and that include two circular-ring-shaped holders  29   a ,  29   b  set apart from each other and connected by a web  31 . With a pin  32  of the tensioning rail  10 , the contours  30  form the pivot  19 . A shift of the pin  32  locked in the holder  29   a  into the holder  29   b  requires a pivot of the tensioning rail  10  into an extreme position in which a cross section set by a flattened section  33  of the pin  32  is produced that is less than a width dimension of the web  31 .  FIG. 5  shows the pin  32  in an enlarged diagram and illustrates the flattened section  33 . 
       FIG. 6  shows, as an individual part, the sub-rail  9  of the guide rail  7  in a perspective view. The sub-rail  9  is supported in the installed state by a contact face  34  on the support face  28  of the base rail and is fixed by the attachment  22 . The sub-rail  9  further includes brackets  14   a ,  14   b  that are set apart from each other and that have projections  15   a ,  15   b  that are directed toward each other and on which the tensioning rail  10  locks for forming the transport securing device  13 . 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Internal combustion engine 
           2  Tensioning means drive 
           3   a  Camshaft 
           3   b  Camshaft 
           4  Drive wheel 
           5   a  Driven wheel 
           5   b  Driven wheel 
           6  Assembly unit 
           7  Guide rail 
           8  Base rail 
           9  Sub-rail 
           10  Tensioning rail 
           11  Holding segment 
           12  Traction element 
           13  Transport securing device 
           14   a  Bracket 
           14   b  Bracket 
           15   a  Projection 
           15   b  Projection 
           16  Tensioning device 
           17  Tensioned section 
           18  Tensioned section 
           19  Pivot 
           20  Slack section 
           21  Leg 
           22  Attachment 
           23  Anti-jumping device 
           24  Anti-jumping device 
           25  Vent 
           26  Jet 
           27  Opening 
           28  Contact 
           29   a  Holder 
           29   b  Holder 
           30  Contours 
           31  Web 
           32  Pin 
           33  Flattened section 
           34  Contact face