Abstract:
The invention relates to a tensioning or deflector pulley, in particular for the belt drive on an internal combustion engine, essentially comprising a plastic or steel running pulley, formed by an inner hub ring, an outer running ring and a pulley disc, connecting both rings to each other, with a radial roller bearing fixed in the hub ring of the running pulley, made up of an inner bearing ring and an outer bearing ring with a number of rolling bodies running between the bearing rings in channeled running tracks, retained at regular separations from each other by a bearing cage with a seal to both sides of the roller bodies, by means of which the cavity, formed between the bearing rings and designed as a grease reservoir, is sealed.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a tensioning or deflector pulley according to the features of patent claim  1  which form the preamble, and it can advantageously be implemented, in particular, on tensioning or deflector pulleys arranged within a belt drive of an internal combustion engine or else on friction wheels for the decoupled water pump drive on internal combustion engines. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is known that the belt drive of an internal combustion engine serves for the drive of auxiliary assemblies of the motor vehicle, such as, for example, the generator, air conditioning compressor or water pump, and is designed, as a rule, as a belt drive driven by the crankshaft of the internal combustion engine. Since the individual auxiliary assemblies, as a consequence of their functions, are arranged offset with respect to one another on the internal combustion engine, the belt drive is provided with deflector pulleys for the belt which deflector pulleys are fastened rotatably to the internal combustion engine and which in each case ensure a sufficient looping around of the belt pulleys of the auxiliary assemblies. At the same time, the required tension of the belt is set with the aid of a tensioning pulley which is likewise fastened rotatably to the internal combustion engine at a pivoting arm acted upon by a spring force. Tensioning or deflector pulleys of this type consist essentially of a plastic or steel running roller which is formed essentially by an inner hub ring and an outer running ring and by a wheel disk connecting the two rings to one another, and of a radial rolling bearing which is fixed in position in the hub ring of the running roller and which consists of an inner bearing ring and an outer bearing ring and of a multiplicity of rolling bodies which roll between the bearing rings in groove-shaped raceways and which are held at uniform distances from one another by a bearing cage. Furthermore, the radial rolling bearing has axially on both sides of its rolling bodies one seal each by means of which the interspace between the bearing rings, which is designed as a grease repository, is sealed off. 
         [0003]    Such a tensioning or deflector pulley is already known as generic, for example, from DE 100 61 995 A1. In the running roller disclosed in this publication, the radial rolling bearing is designed in the usual way as a single-row grooved ball bearing which is cast with its outer bearing ring into the hub ring of the running roller consisting of plastic. The rolling bodies of this grooved ball bearing in this case consist of a defined number of bearing balls which roll in groove-shaped raceways in the inner and in the outer bearing ring and which are held at uniform distances from one another by means of a bearing cage. The interspace between the bearing rings which is designed as a grease repository is sealed off by means of what is known as a two-stage seal, the first stage of which consists in each case of a reinforced lip seal and the second stage of which is formed in each case by a further sealing disk axially preceding the first stage with an annular sealing gap. 
         [0004]    The lip seals are thus in each case fixed in position in an annular slot at the outermost margin in the inside of the outer bearing ring and, brushing via an elastic sealing lip, are supported in each case in a peripheral slot at the outermost margin in the outside of the inner bearing ring of the radial rolling bearing. By contrast, the further sealing disk is designed as a separate annular metal disk which is plugged with its inside diameter on a head-side centering extension of the fastening screw of the running roller and which is braced between the inner bearing ring and the screw head of the fastening screw. At the same time, the sealing disk extends radially over the entire height of the interspace between the bearing rings of the radial rolling bearing and on its outer circumference has an elastic sealing lip which is supported on the axial end face of the outer bearing ring. 
         [0005]    The disadvantage of this known tensioning pulley, however, is that the grooved ball bearing used for its mounting, particularly on high-performance and high-torque internal combustion engines, comes up against the limits of its load-bearing capacity more and more often due to the high operating forces and is consequently subjected to increased wear, because of which the grooved ball bearing has to be exchanged prematurely. The cause of the limited load-bearing capacity of such a grooved ball bearing is in this case to be seen in the limited number of mountable bearing balls which, in such bearings, are introduced by what is known as the eccentric mounting method, in which the two bearing rings are arranged eccentrically to one another, the free space thereby occurring between the bearing rings is filled with the bearing balls, and, thereafter, the inner bearing ring is brought into the position concentric to the outer bearing ring, utilizing the elasticity of the two bearing rings. Finally, the bearing balls are distributed uniformly in the raceways of the bearing rings, and the bearing cage is inserted, and therefore it is, as a matter of course, impossible to fill the bearing fully with bearing balls by means of this mounting method. 
         [0006]    Even the obvious possibility of increasing the load-bearing capacity of the tensioning or deflector pulley using two-row grooved ball bearings is limited, mostly because of construction space, at least in passenger vehicles, and therefore two-row grooved ball bearings are employed preferably for the tensioning and deflector pulleys of the belt drive of commercial vehicles, but, even in these, often come up against the limits of their load-bearing capacity because of increasingly higher-performance internal combustion engines. 
         [0007]    It is also a disadvantage, in the grooved ball bearing used in the known tensioning pulley, that its available grease repository for lubricating the bearing has a relatively small design. Since, as a consequence of construction, no relubrication possibilities are provided for the radial rolling bearings of tensioning and deflector pulleys, the useful life of the grooved ball bearing is therefore also dependent on the size or possible period of use of the existing grease repository. The size of the grease repository is in this case defined by the free volume of the interspace between the bearing rings which, in the grooved ball bearing used, is reduced considerably due to the volume of the bearing balls and of the bearing cage and, at least in grooved ball bearings with standard dimensions, also cannot be extended without major expenditure. 
         [0008]    Finally, even the two-stage sealing of the grooved ball bearing of the known tensioning pulley has proved to be a disadvantage in that the further sealing disks preceding the inner lip seals are designed as separate individual parts which are delivered together with the tensioning pulley and constitute the intended functional unit with the lip seals only when the tensioning pulley is being screwed to the internal combustion engine by the final manufacturer. However, such designs in a differential type of construction no longer conform to the present-day requirements of the automotive industry in terms of system solutions from the supply industry, whereby, in this particular case, the tensioning pulley is designed as an integral component with all seals, which merely has to be finally mounted as a functioning module on the internal combustion engine. 
       OBJECT OF THE INVENTION 
       [0009]    Proceeding from the outlined disadvantages of the known prior art, the object on which the invention is based, therefore, is to design a tensioning or deflector pulley, in particular for the belt drive of an internal combustion engine, which is mounted on a radial rolling bearing with standard dimensions which has increased load-bearing capacity and an enlarged grease repository and is therefore distinguished by lower wear and an increased useful life, and which additionally has a seal, designed in an integral type of construction, of the interspace between the bearing rings. 
       DESCRIPTION OF THE INVENTION 
       [0010]    According to the invention, in a tensioning or deflector pulley according to the preamble of claim  1 , this object is achieved in that the radial rolling bearing is designed as a spherical roller bearing, the rolling bodies of which are designed as spherical rollers, each with two side faces flattened symmetrically from a basic spherical shape and arranged parallel to one another, the spherical roller bearing having, in relation to a comparable ball bearing, an increased load-bearing capacity due to the higher number of mountable rolling bodies and, at the same time, an enlarged grease repository due to the reduced construction space of the rolling bodies. 
         [0011]    Preferred embodiments and advantageous developments of the tensioning or deflector pulley designed according to the invention are described in the subclaims. 
         [0012]    Thus, according to claim  2 , in the tensioning or deflector pulley designed according to the invention, there is provision for the rolling bodies of the radial rolling bearing which are designed as spherical rollers to have preferably a width between their side faces of about 70% of their basic spherical shape. At the same time, the width of the raceways in the bearing rings likewise amounts to at least 70% of the diameter of the basic spherical shape of the spherical rollers, so that their running faces have, under radial load, one hundred percent linear contact with the raceways in the bearing rings. Designing the spherical rollers and the raceways with such a width has thereby proved appropriate, in practice, with regard to the radial and axial load-bearing capacity of the bearing and corresponds approximately to the contact area which the balls of conventional grooved ball bearings also have with their raceways in the bearing rings. The distance between the bearing rings has, correspondingly, a magnitude of about 80% of the diameter of the basic spherical shape of the rolling bodies, so that the spherical rollers can first be introduced axially into the radial rolling bearing in a horizontal position through the clearance between the bearing rings arranged concentrically to one another and can then be pivoted by a vertical and a horizontal rotation by 90°, each. Proceeding from this, therefore, as claimed in claim  3 , one of the characterizing features of the tensioning or deflector pulley designed according to the invention is that the radial rolling bearing designed as a spherical roller bearing has, in relation to a comparable ball bearing, 30% to 40% more rolling bodies and a correspondingly higher load-bearing coefficient and, at the same time, due to the flattened side faces of the rolling bodies, a between 20% and 30% larger grease repository in the interspace between the bearing rings. At the same time, the higher number of rolling bodies makes it possible to have an up to three times higher load-bearing coefficient in relation to comparable ball bearings, while the larger grease repository additionally prolongs the useful life of bearings of this type by 1.3 to 1.5 times that of comparable ball bearings. 
         [0013]    Furthermore, the set object with regard to sealing the interspace between the bearing rings is achieved according to the invention, as claimed in claims  4  to  6 , in that the seal, arranged axially on both sides of the rolling bodies of the radial rolling bearing, is preferably designed as a two-stage seal, the first stage of which consists in each case of a reinforced lip seal known per se, but the second stage of which is formed in each case by a further sealing disk axially preceding the first stage with an annular sealing gap and which can be preassembled, together with the lip seal, as a functional module by the tensioning pulley manufacturer. 
         [0014]    The lip seals, preferably reinforced by a sheet metal or plastic ring and consisting of an elastomer, are thereby, on the one hand each fixed in position in an annular slot in the inside of the outer bearing ring, which annular slot can be arranged, offset slightly axially inward with respect to the rolling bodies, due to the narrow design of the rolling bodies. On the other hand, in a likewise known way, the lip seals, brushing via one or more elastic sealing lips, are each supported in a peripheral slot in the outside of the inner bearing ring of the radial rolling bearing, which peripheral slot is likewise arranged so as to be offset slightly with respect to the rolling bodies. 
         [0015]    By contrast, the further sealing disks of the seal, which are preferably produced from a metallic material in a non-cutting manner, have a simple annular shape, with each an annular rim, which is located on the inside-diameter side and by means of which the sealing disks are fastened, preferably nonpositively, on the marginal portions of the outside of the inner bearing ring which are free due to the fact that the lip seals are offset inward. The annular rim on the sealing disks is thereby advantageously arranged so as to point to the axial sides of the radial rolling bearing and to be flush with these, so that the sealing disks can be fastened in a particularly cost-effective way by being pressed onto the inner bearing ring, and they form an integral component of the tensioning or deflector pulley. 
         [0016]    Finally, as an advantageous embodiment of the inclined rolling bearing designed according to the invention, it is also proposed, by claims  7  and  8 , that the further sealing disks of the seal extend radially virtually over the entire magnitude of the distance between the bearing rings and, to improve the sealing action, selectively also have on the outside-diameter side additional elastic sealing lips which are connected sealingly to the marginal portions of the inside of the outer bearing ring which are free due to the fact that the lip seals are offset inward. If even a water-resistant fordable seal of the radial rolling bearing is thereby to be achieved, it is also optionally possible, furthermore, to additionally insert into the annular sealing gaps between the lip seals and the sealing disks of the seal, in a known way, a continuous grease bead or felt ring which at least partially fills the sealing gap. 
         [0017]    The tensioning or deflector pulley designed according to the invention thus has the advantage, as compared with the tensioning or deflector pulleys known from the prior art, that it is mounted on a radial rolling bearing designed as a spherical roller bearing, with standard dimensions, which, due to the increased number and the narrow type of construction of the mountable rolling bodies, has a substantially higher load-bearing capacity and, at the same time, an enlarged grease repository in relation to a comparable ball bearing and which is therefore distinguished by lower wear and an increased useful life. In addition, the spherical roller bearing of the tensioning or deflector pulley designed according to the invention has a seal of the interspace between the bearing rings, which seal is designed in an integral type of construction and can be preassembled, complete, by the tensioning pulley manufacturer and, optionally, designed to be fordable. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]    The tensioning or deflector pulley designed according to the invention is explained in more detail below by means of two preferred embodiments, with reference to the accompanying drawings in which: 
           [0019]      FIG. 1  shows a cross section through a tensioning pulley designed according to the invention, mounted on a single-row spherical roller bearing; 
           [0020]      FIG. 2  shows a cross section through a tensioning pulley designed according to the invention, mounted on a two-row spherical roller bearing; 
           [0021]      FIG. 3  shows an enlarged illustration of a cross-sectional half of the single-row spherical roller bearing according to  FIG. 1 ; 
           [0022]      FIG. 4  shows an enlarged illustration of a cross-sectional half of the two-row spherical roller bearing according to  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       [0023]    A tensioning pulley  1  for the belt drive of an internal combustion engine may be gathered clearly from  FIGS. 1 and 2  each and has a plastic or steel running roller  2  which is formed essentially by an inner hub ring  3  and an outer running ring  4  and by a wheel disk  5  connecting the two rings  3 ,  4  to one another. Furthermore, one radial rolling bearing  6  each is fixed in position in the hub ring  5  of the running rollers  2  depicted, which rolling bearing consists of an inner bearing ring  7  and an outer bearing ring  8  and of a multiplicity of rolling bodies  12  or  12 ,  12 ′ which are arranged between the bearing rings  7 ,  8  and which roll either in one row in groove-shaped raceways  9 ,  10  or in two rows in groove-shaped raceways  9 ,  9 ′,  10 ,  10 ′ and are held at uniform distances from one another by means of a bearing cage  11  or two bearing cages  11 ,  11 ′. Moreover, each radial rolling bearing  6  has axially on both sides of its rolling bodies  12  or  12 ,  12 ′ in each case a seal  13 ,  14 , by means of which the interspace  15  between the bearing rings  7 ,  8 , which is designed as a grease repository, is sealed. As can be seen clearly, the tensioning pulleys  1  are then fastened in each case via the inner bearing ring  7  of their radial rolling bearings  6  which is centered on a receptacle  16  of a housing  17  and which is screwed to this housing by means of a fastening screw  18 . 
         [0024]    Furthermore, it may be gathered from  FIGS. 1 and 2  that the radial rolling bearings  6  shown are in each case designed, according to the invention, as spherical roller bearings, the rolling bodies  12  or  12 ,  12 ′ of which are designed as spherical rollers, each with two side faces  19 ,  20  or  19 ,  19 ′,  20 ,  20 ′ flattened symmetrically from a basic spherical shape and arranged parallel to one another. These rolling bodies  12  designed as spherical rollers have a width between their side faces  19 ,  20  or  19 ,  20  and  19 ′,  20 ′ of about 70% of the diameter of their basic spherical shape and are first introduced axially into the radial rolling bearing  6  in a horizontal position, between the bearing rings  7 ,  8  arranged concentrically to one another, through the clearance  21  having a magnitude of about 80% of the diameter of the basic spherical shape of the rolling bodies  12  and are then pivoted by a vertical and a horizontal rotation by 90° each, into the raceways  9 ,  10  of the bearing ring  7 ,  8 . This mounting possibility and the flattened side faces  19 ,  20  or  19 ,  20  and  19 ′,  20 ′ of the rolling bodies  12  have the effect that the radial rolling bearings  6  designed as spherical roller bearings have, in relation to comparable ball bearings, 30% to 40% more rolling bodies  12  and a correspondingly higher load-bearing coefficient and, at the same time, a between 20% and 30% larger grease repository in the interspace  15  between the bearing rings  7 ,  8 . 
         [0025]    Furthermore, it becomes clear from  FIGS. 3 and 4  that the seal  13 ,  14 , arranged axially on both sides of the rolling bodies  12 , of the radial rolling bearings  6  is designed in each case as a premountable two-stage seal, the first stage of which consists in each case of a reinforced lip seal  22 ,  23  and the second stage of which is formed in each case by a further sealing disk  24 ,  25  axially preceding the first stage with an annular sealing gap  26 ,  27 . The lip seals  22 ,  23 , reinforced by a metal or plastic ring not designated in any more detail, are at the same time each fixed in position in an annular slot  28 ,  29 , offset axially inward with respect to the rolling bodies  12 , in the inside of the outer bearing ring  8  and, brushing via a plurality of elastic sealing lips  30 ,  31 , are each supported in a peripheral slot  32 ,  33  in the outside of the inner bearing ring  7  of the radial rolling bearing  6 . 
         [0026]    By contrast, the further sealing disks  24 ,  25  of the seal  13 ,  14 , which are produced from a metallic material in a non-cutting manner, have an annular shape, in each case with an annular rim  34 ,  35  which is located on the inside-diameter side and by means of which the sealing disks  24 ,  25  are pressed onto the marginal portions  36 ,  37  of the outside of the inner bearing ring  7  which are free due to the fact that the lip seals  22 ,  23  are offset inward. As can be seen clearly, these further sealing disks  24 ,  25  of the seal  13 ,  14  extend radially at the same time virtually over the entire magnitude of the distance  21  between the bearing rings  7 ,  8  and additionally have on the outside-diameter side elastic sealing lips  40 ,  41  which are connected sealingly to the marginal portions  38 ,  39  of the inside of the outer bearing ring  8  which are free due to the fact that the lip seals  22 ,  23  are offset inward. In addition, a continuous grease bead  42 ,  43  is inserted into the annular sealing gap  26 ,  27  between the lip seals  22 ,  23  and the sealing disks  24 ,  25  of the seal  13 ,  14  and at least partially fills the sealing gap  26 ,  27  and gives rise to a water-resistant fordable seal  13 ,  14  of the radial rolling bearing  6 . 
       LIST OF REFERENCE NUMERALS 
       [0027]      1  Tensioning pulley
   2  Running roller
   3  Hub ring of  2     4  Running ring of  2     5  Wheel disk of  2     6  Radial rolling bearing
   7  Inner bearing ring of  6     8  Outer bearing ring of  6   
         9 ,  9 ′ Raceway in  7   
       10 ,  10 ′ Raceway in  8   
       [0028]      11 ,  11 ′ Bearing cage of  6     12 ,  12 ′ Rolling body of  6   
         13  Seal of  6   
       14  Seal of  6   
       [0029]      15  Interspace between  7  and  8   
         16  Receptacle 
       17  Housing 
       [0030]      18  Fastening screw
   19 ,  19 ′ Side face of  12 ,  12 ′
   20 ,  20 ′Side face of  12 ,  12 ′
   21  Distance between  7  and  8     22  Lip seal of  13     23  Lip seal of  14     24  Sealing disk of  13     25  Sealing disk of  14     26  Sealing gap between  22  and  24     27  Sealing gap between  23  and  25     28  Annular slot for  22     29  Annular slot for  23     30  Sealing lips of  22     31  Sealing lips of  23     32  Peripheral slot for  30     33  Peripheral slot for  31   
         34  Annular rim on  24   
       35  Annular rim on  25   
       [0031]      36  Free marginal portion of  7     37  Free marginal portion of  7     38  Free marginal portion of  8     39  Free marginal portion of  8   
         40  Sealing lip on  24   
       41  Sealing lip on  25   
       [0032]      42  Grease bead in  26     43  Grease bead in  27