Abstract:
A tensioning rail ( 2 ) for tensioning an endlessly circulating tensioner ( 4 ) is provided, wherein the tensioning rail ( 2 ) for tensioning the ternsioner ( 4 ) is curved in a longitudinal direction (L), the tensioning rail ( 2 ) has a base wall ( 6 ) and two jaws ( 8 ) protruding from the base wall ( 6 ), and the tensioning rail ( 2 ) has at least one U-shaped profiled segment ( 10 ) and a T-shaped profiled segment ( 12 ), which are each formed by the base wall ( 6 ) and the jaws ( 8 ), wherein the tensioning rail ( 2 ) includes a guiding element ( 14 ) for a rotary bearing ( 16 ) in the U-shaped profiled segment ( 10 ) and a guiding element ( 18 ) for a contact bearing ( 20 ) in the T-shaped profiled segment ( 12 ).

Description:
[0001]    The present invention relates to a tensioning rail for tensioning a continuously revolving traction mechanism, the tensioning rail for tensioning the traction mechanism being arched in the longitudinal direction, the tensioning rail including a base wall and two cheeks protruding from the base wall, and the tensioning rail including at least one U-shaped profile section and one T-shaped profile section, each of which is formed by the base wall and the cheeks. 
         [0002]    Moreover, the present invention encompasses a traction mechanism drive which includes a drive wheel situated on a drive shaft of an internal combustion engine, at least one driving wheel, a continuously revolving traction mechanism which encompasses the drive wheel and the at least one driving wheel, a tensioning rail of the above-mentioned type, and a tensioning device for transmitting a tension force to the tensioning rail. 
       BACKGROUND 
       [0003]    Tensioning rails are preferably used for traction mechanism drives of internal combustion engines, such as gasoline engines or diesel engines of motor vehicles. However, they may also be used in watercraft or aircraft. The continuously revolving traction mechanism used is often designed as a chain or belt. When a chain is used, it is preferably made up of steel links. 
         [0004]    The traction mechanism is situated between different shafts, for example between a crankshaft, one or multiple intermediate shafts, and/or one or multiple camshafts, for the force transmission. Thus, for example, force transmission may take place from a drive wheel, such as that of a crankshaft, to a driving wheel, such as that of a camshaft. 
         [0005]    Due to the frequently fluctuating load on the traction mechanism, it is advantageous to tension the traction mechanism. For this purpose, the tensioning rail is pressed against the continuously revolving traction mechanism until the traction mechanism reaches the desired pretension. The tensioning rail generally presses on the slack span of the traction mechanism, so that the traction mechanism slides across the tensioning rail. It has proven to be advantageous if the tensioning rail is arched in the longitudinal direction. Thus, it is not possible for the traction mechanism to jam in the tensioning rail. 
         [0006]    The tensioning rail includes a base wall and two cheeks which protrude from the base wall. The base wall at its front side may come into contact with the traction mechanism in order to tension it. The base wall facing the front side, i.e., transversely with respect to the longitudinal direction of the guide rail, often is likewise arched. In addition, on the front side the base wall may include a slide lining which comes into contact with the traction mechanism. The cheeks generally protrude from the rear side of the base wall. The cheeks are preferably situated in parallel to one another and/or symmetrically with respect to the tensioning rail. The cheeks are used for increasing the stability of the tensioning rail. In addition, the cheeks provide an advantageous option for transmitting forces for tensioning the traction mechanism to the tensioning rail. 
         [0007]    Furthermore, it is provided that the tensioning rail includes at least one U-shaped profile section and one T-shaped profile section, each of which is formed by the base wall and the cheeks. A tensioning rail including profile sections of this type is known from Published Unexamined Patent Application US 2012/0015769 A1. A U-shaped profile section is situated between two T-shaped profile sections, viewed in the longitudinal direction. The two T-shaped profile sections each include a cross-hole for a pivot bearing. Due to the shape transition from the U-shaped profile to the particular T-shaped profile, the T-shaped profile sections are particularly advantageously suited for introducing tension forces into the tensioning rail. In practice, however, it has been found that, due to the small width of the guide rail in the particular T-shaped profile section and the cross-hole formed there for the pivot bearing, there is a risk that during operation the guide rail may tilt slightly about a longitudinal axis. To preferably prevent this, the guide rail must be manufactured very precisely. The level of effort for manufacturing such a guide rail is therefore very high. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a tensioning rail, which is preferably easily and cost-effectively manufacturable as well as dimensionally stable and functionally reliable, for tensioning a continuously revolving traction mechanism. Moreover, and alternate or additional object of the present invention is to provide a traction mechanism drive which includes such a tensioning rail. 
         [0009]    The present invention provides that the tensioning rail includes a guide element for a pivot bearing in the U-shaped profile section. For the U-shaped profile section, the cheeks are spaced apart from one another. A guide element for the pivot bearing in this U-shaped profile section therefore has a particularly effective action against a torque about a longitudinal axis of the tensioning rail. The tensioning rail is therefore particularly robust against tilting about a longitudinal axis of the tensioning rail. 
         [0010]    For the tensioning rail according to the present invention, it is provided that the tensioning rail in the T-shaped profile section has an enlarged contact area for contacting a tensioning device which is formed by a spacer piece inserted between the cheeks. In the T-shaped profile section, the cheeks are situated directly next to one another and/or contact one another. Due to the T-shaped design of the profile and due to the transition from the U-shaped profile section to the T-shaped profile section, the tensioning rail in the T-shaped profile section has a particularly stable design. The T-shaped profile section is therefore preferably suitable for transmitting a tension force from a tensioning device to the tensioning rail. Since the contact area is also enlarged due to the distance between the cheeks and the inserted spacer piece, the risk of the tensioning device losing contact with the tensioning rail after an extended operating period and/or under adverse operating conditions may be significantly reduced. In addition, the tension force may be transmitted in a functionally reliable manner and with lower maximum component stress on the tensioning rail in the region of the contact area. Within the context of the present invention, a contact bearing is understood to mean a bearing which results when the transmission element of the tensioning device is brought together with the spacer piece of the guide rail. The transmission element may be placed on the spacer piece for the contact bearing. When the transmission element is merely placed on the guide element for the contact bearing, it is possible for the T-shaped profile section to be acted on by the tension force only in the direction perpendicular to the T-shaped profile section. The contact bearing is therefore in particular a floating bearing. Other conceivable guide forces, such as in the transverse direction, may be disregarded in this case. 
         [0011]    Since a U-shaped profile section and a T-shaped profile section are provided for the tensioning rail according to the present invention, the manufacture of the tensioning rail according to the present invention is particularly simple and cost-effective. At the same time, due to the guide element for the pivot bearing being situated in the U-shaped profile section, the tensioning rail according to the present invention is very dimensionally stable and robust against possible tilting about a longitudinal axis. 
         [0012]    According to one preferred embodiment of the tensioning rail, it is provided that the base wall and the cheeks are one piece. The base wall and the cheeks may thus be designed in one piece. The manufacture is particularly simple and cost-effective, since the base wall and the cheeks may be produced, for example, from a blank with the aid of a pressing process. The associated deflections impart high stability and rigidity to the tensioning rail. 
         [0013]    One preferred embodiment of the tensioning rail is characterized in that the spacer piece for the contact bearing is formed by a cylindrical pin. Due to the circular cross section, the provided design of the spacer piece as a cylindrical pin results in a circular contact area via which the tensioning rail may be prevented from sliding off the transmission element of the tensioning device particularly well, independently of direction. In addition, the receptacle for the spacer piece, having a corresponding shape, may be formed by two half-shells of the cheeks which together form a cylindrical receptacle. In the area of the receptacle, the cheeks therefore have the largest possible radius, which results in the lowest possible, uniform component stress on the cheeks and the spacer piece, in particular when the cylindrical pin is pressed in. In addition, except for the position of its longitudinal axis, the cylindrical pin does not have to be situated in a certain orientation in the receptacle, as the result of which an automated assembly of the tensioning rail may be simplified. 
         [0014]    One preferred embodiment of the present invention is characterized in that the spacer piece for the contact bearing forms a flush surface with the end faces. A further enlarged flat contact area may be provided due to the provided approach, since the end faces of the cheeks may thus additionally be utilized for transmitting force from the tensioning device to the tensioning rail. 
         [0015]    According to one alternative embodiment of the present invention, it is provided that the spacer piece protrudes beyond the T-shaped profile section of the tensioning rail. It may thus be ensured in a particularly easy manner that a transmission element of the tensioning device comes into contact with the spacer piece, i.e., with the provided contact area, in order to form the contact bearing, and does not instead come into contact with the end faces of the cheeks. 
         [0016]    It is further provided that the spacer piece for the contact bearing is a metal pin, in particular a steel pin, and that the material of the tensioning rail is softer than that of the spacer piece. The provided metal pin has a particularly high stability, and due to its high stability may be pressed in particularly easily between the cheeks of the T-shaped profile section. For increasing the stability or hardness, the metal pin or steel pin may additionally be subjected to heat treatment. 
         [0017]    In particular, the spacer piece may have a spherical segment-shaped contact area for force absorption, so that a force transmission from the tensioning device from different force directions is possible. This is particularly advantageous due to the fact that the tensioning rail is at least slightly pivoted during the tensioning, while the tensioning device, and thus also a piston of the tensioning device which contacts the contact area, has a fixed, unchangeable orientation. 
         [0018]    Another preferred embodiment of the present invention is characterized in that the T-shaped profile section is situated between two U-shaped profile sections. This ensures that the tensioning rail is particularly dimensionally stable and/or robust against unintentional deflections. In addition, for a tensioning rail which includes such profile sections, particularly high forces may be transmitted from the tensioning device to the T-shaped profile section. 
         [0019]    In the area of the U-shaped profile section of the tensioning rail, mutually coaxially situated boreholes which together form the guide element for a pivot bearing may be provided in the cheeks. In addition, a socket which is intended for the pivot bearing and/or which forms a part of this pivot bearing may be embedded in these boreholes. The pivot bearing may thus be manufactured particularly easily and precisely. 
         [0020]    According to another aspect, the object of the present invention is achieved by a traction mechanism drive which includes a drive wheel situated on a drive shaft of an internal combustion engine, at least one driving wheel, a continuously revolving traction mechanism which encompasses the drive wheel and the at least one driving wheel, a tensioning rail according to the present invention, and a tensioning device for transmitting a tension force to the tensioning rail. 
         [0021]    Features, details, and advantages described in conjunction with the tensioning rail according to the present invention naturally also apply in conjunction with the traction mechanism drive according to the present invention, and in each case conversely, so that reciprocal reference is or may always be made with regard to the disclosure of the individual aspects of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The present invention is explained below with reference to the appended figures. 
           [0023]      FIG. 1  shows a traction mechanism drive according to the present invention, including a tensioning rail for tensioning a traction mechanism; 
           [0024]      FIG. 2  shows a first perspective view of the tensioning rail according to the present invention; 
           [0025]      FIG. 3  shows a second perspective view of the tensioning rail according to the present invention; and 
           [0026]      FIG. 4  shows another perspective view of the tensioning rail according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  shows a traction mechanism drive  3  according to the present invention, including a drive wheel  34  situated on a shaft  32  of an internal combustion engine (not illustrated), and including a drive wheel  36 . In principle, multiple drive wheels  34  may be provided. Traction mechanism drive  3  includes a continuously revolving traction mechanism  4  which encompasses drive wheel  34  and the at least one drive wheel  36 . Due to traction mechanism  4  which is in engagement with drive wheel  34  and with drive wheel  36 , mechanical power may be transferred from drive wheel  34  to drive wheel  36 . The same applies for the shafts connected in each case. Traction mechanism  4  is generally designed as a chain or as a belt. If a chain is used, gearwheels are employed as wheels. 
         [0028]    To ensure a secure revolution of traction mechanism  4 , it has proven to be advantageous to tension traction mechanism  4 . For this purpose, a tensioning rail  2  as illustrated in  FIGS. 2 through 4  is pressed against continuously revolving traction mechanism  4  until traction mechanism  4  reaches the desired pretension. Tensioning rail  2  generally presses with a front side of a base wall  6  on slack span  42  of traction mechanism  4 , so that traction mechanism  4  slides across tensioning rail  2  during operation. It has proven to be advantageous if tensioning rail  2  or base wall  6  is arched in longitudinal direction L. In other words, the front side of base wall  6  has a convex design. Thus, it is not possible for traction mechanism  4  to jam in tensioning rail  2  or in base wall  6 . In addition, a fairly large contact surface for traction mechanism  4  is achieved on the front side. It may advantageously also be provided that tensioning rail  2  or base wall  6  has an arched configuration and/or design in the transverse direction on the front side facing traction mechanism  4 . This ensures a particularly problem-free operation. 
         [0029]    Base wall  6  of tensioning rail  2  is advantageously planar, so that a longitudinal extension and/or a transverse extension of base wall  6  in each case is greater than a thickness or height of base wall  6 . To increase the dimensional stability of tensioning rail  2 , two cheeks  8  which protrude from base wall  6  are provided for tensioning rail  2 , whereby cheeks  8  and base wall  6  have such a contour in longitudinal direction L of tensioning rail  2  that together they form at least one U-shaped profile section  10  and at least one T-shaped profile section  12 . Due to the corresponding contour, base wall  6  and cheeks  8  of tensioning rail  2  already impart an increased dimensional stability. In addition, cheeks  8  protrude from base wall  6 , in particular preferably at a right angle or at an acute angle between  20  degrees and  90  degrees, for example, so that cheeks  8  are robust against tension forces. A parallel orientation of cheeks  8  in U-shaped profile section  10  and/or in T-shaped profile section  12  also ensures a good force distribution on base wall  6 . Cheeks  8  may be connected to one another in T-shaped profile section  12  in an integrally joined, form-locked, and/or force-fit manner. This increases the torsional rigidity of tensioning rail  2 . Cheeks  8  are advantageously situated on a rear side or on a side of base wall  6  facing away from traction mechanism  4 . This configuration ensures a particularly simple introduction of tension forces and prevents cheeks  8  from jamming on traction mechanism  4 . 
         [0030]    U-shaped profile section  10  formed by cheeks  8  includes a guide element  14  for a pivot bearing  16 . A corresponding rotation axis D is oriented transversely with respect to a longitudinal direction L of tensioning rail  2 . When tensioning rail  2  is used for traction mechanism drive  4 , tensioning rail  2  is rotatably fastened to a bearing counterpart, for example a shaft, of the pivot bearing with the aid of guide element  14 . Such bearing counterparts for pivot bearings are known from the prior art. When tensioning rail  2  is assembled or installed, guide element  14  may be regarded as part of pivot bearing  16 . In the area of guide element  14 , cheeks  8  which are spaced apart from one another ensure high torsional rigidity of tensioning rail  2  about its longitudinal axis L. When tensioning rail  2  is rotatably fastened to the bearing counterpart, cheeks  8  ensure a precise alignment of tensioning rail  2 . This ensures a problem-free operation. 
         [0031]    As is apparent from  FIG. 3 , cheeks  8  have a cross-hole  44  in each of U-shaped profile sections  10 . Cross-holes  44  are aligned coaxially with respect to one another. In a simple embodiment, these cross-holes  44  may form guide element  14  in U-shaped profile section  10  of tensioning rail  2 . 
         [0032]    An alternative or expanded embodiment of guide element  14  in U-shaped profile section  10  of tensioning rail  2  is illustrated in  FIG. 4 . A cylindrical sleeve  46  extends between cheeks  8 . Sleeve  46  may adjoin boreholes  44  and/or may be bordered by same. Sleeve  46  is preferably joined to cheeks  8  in an integrally joined, force-fit, and/or form-locked manner. In this case, sleeve  46  and/or boreholes  44  form guide element  14  in U-shaped profile section  10  of tensioning rail  2 . The stability of tensioning rail  2  is further increased when sleeve  46  is made of a hardened material such as steel. In addition, sleeve  46  is particularly resistant and undergoes little wear. 
         [0033]    It is apparent from  FIG. 3  that in one section, tensioning rail  2  in T-shaped profile section  12  has a receptacle  22  made up of two half-shells in which a spacer piece  18  for a contact bearing  20  is provided. Spacer piece  18  for contact bearing  20  is designed as a cylindrical pin, while receptacle  22  is circular. As likewise shown in  FIG. 3 , receptacle  22  is shaped or formed by cheeks  8 . Similarly, receptacle  22  may have a two-part design. If cheeks  8  are produced from a flat blank by a shaping process, in particular with the aid of bending, receptacle  22  may also be produced in a particularly simple way. For this purpose, a corresponding cylindrical negative mold may be used to place cheeks  8  in T-shaped profile section  12 . The negative mold may be subsequently removed. 
         [0034]    Cylindrical receptacle  22  is open at an end-face side so that spacer piece  18 , which is formed here by a metal pin, particularly preferably a steel pin, and introduced into receptacle  22 , may be pressed in. The opposite end-face side of receptacle  22  preferably includes a stop which is formed by base wall  6  and/or by receptacle  22  itself. 
         [0035]    In  FIG. 4 , receptacle  22  explained above is expanded by metal pin  18 , particularly preferably a steel pin, which is bordered by receptacle  22 . The metal pin is dimensioned with respect to length and formed on the end-face side in such a way that a flush surface results as a complement to the end faces of cheeks  8 . Alternatively, the metal pin may be slightly longer than receptacle  22  so that it protrudes slightly beyond the longitudinal edges of cheeks  8  in the area of receptacle  22 , and tensioning device  2  may be brought into contact with metal pin  18  in a particularly simple manner. Metal pin  18  is used for absorbing and transmitting tension forces from tensioning device  24  to traction mechanism  4  via tensioning rail  2 . The robustness of tensioning rail  2  is increased due to metal pin  18 , in particular when metal pin  18  is particularly hardened and/or has a high rigidity. 
         [0036]    The end face which forms contact area  30  of spacer piece  18 , or, in the present exemplary embodiment, of metal pin  18 , may preferably have a spherical segment-shaped design, so that the introduction of force into spacer piece  18  and the associated component stresses on spacer piece  18  are preferably independent of direction. Alternatively, the end face of the spacer piece may be oriented flatly and in particular perpendicularly with respect to the longitudinal axis of the spacer piece, so that a preferably flat contact area may be achieved as a complement to the end faces of the cheeks. 
         [0037]    The spacer piece  18  may be pressed, glued, or fastened in receptacle  22  in some other way, so that the spacer piece is preferably held captively on tensioning rail  2  after installation. In addition, receptacle  22  and spacer piece  18  may also have other cross-sectional shapes, which may also be adapted to the shape of the adjoining transmission elements of tensioning device  24 . Furthermore, the shape of spacer piece  18  may also be designed for a simple and cost-effective manufacturing method, and may already be inserted between cheeks  8  during the shaping of tensioning rail  2 , so that spacer piece  18  itself virtually forms the negative shape of receptacle  22 , and receptacle  22  is virtually pressed against spacer piece  18  during the shaping. 
         [0038]    Spacer piece  18  may also be formed from a hardening filler compound, which is pressed into receptacle  22  as a shapeable compound and does not harden into a solid body until it is in receptacle  22 . In addition, spacer piece  18  may also be designed as a cover or lid which is placed, screwed, or mounted in some other way on receptacle  22 , and which at least partially covers the end faces of cheeks  8 . In the design of spacer piece  18 , it is important only that spacer piece  18  at least partially closes receptacle  22  which is open toward the outside, so that the surface area of receptacle  22  may be utilized, at least partially, as a contact area for the transmission element of tensioning device  24 . 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           2  tensioning rail 
           3  traction mechanism drive 
           4  traction mechanism 
           6  base wall 
           8  cheeks 
           10  U-shaped profile section 
           12  T-shaped profile section 
           14  guide element 
           16  pivot bearing 
           18  spacer piece 
           20  contact bearing 
           22  receptacle 
           24  tensioning device 
           30  contact area 
           34  drive wheel 
           36  driving wheel 
           38  shaft 
           40  shaft 
           42  slack span 
           44  cross-hole 
           46  sleeve 
         D rotation axis 
         L longitudinal direction of the tensioning rail