Patent Publication Number: US-2022235858-A1

Title: Belt pulley decoupler with axial toothing on both sides and auxiliary unit drive

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2020/100234 filed Mar. 25, 2020, which claims priority to DE 102019113443.9 filed May 21, 2019, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a belt pulley decoupler for arrangement on a crankshaft of an internal combustion engine having a hub, which is provided for coupling to the crankshaft, and a connecting flange, which is in abutment with the hub with a distal face to generate torque from the hub (for example via a spring) to be transmitted to a belt pulley body. The disclosure further relates to an auxiliary unit drive for a motor vehicle having an internal combustion engine and a belt pulley decoupler according to the disclosure. 
     BACKGROUND 
     Belt pulley decouplers or torsional vibration dampers with Hirth toothings are already known from the prior art. In particular, the generic DE 10 2008 064 341 B4 discloses a belt pulley for a belt drive having a hub, a belt pulley ring with at least one circumferential groove for a belt of the belt drive, a torsional vibration damper, and an overrunning clutch arranged between the hub and the belt pulley ring. Complementary Hirth toothings are formed on the hub and on an end section of a crankshaft of an internal combustion engine. 
     The generic DE 10 2017 115 466 A1 also discloses a belt pulley decoupler for arrangement on a crankshaft of an internal combustion engine, having a hub which is intended to be coupled to the crankshaft in a rotationally fixed manner, and a flange element arranged at least partially radially outside of the hub on which a torque introduced from the crankshaft to the hub can be transmitted, and which is provided for least partially transmitting the introduced torque to a belt pulley body with the interposition of a bow spring, wherein the flange element has an inner flange section and an outer flange section configured separately therefrom. In this case, a wave or ramp shape running at least in sections in the circumferential direction of the outer flange section in the manner of an axially acting spur toothing, in particular as a Hirth toothing, can be formed on the outer flange section. 
     However, the prior art still has the disadvantage that increasing torques to be transmitted result in a change in the screw connections on the belt pulley decoupler, which in turn entails additional costs due to design measures. As an alternative to changing the screw connection, secondary measures associated with additional costs, such as coatings that increase the coefficient of friction, friction foils or diamond foils, etc., are usually used 
     SUMMARY 
     It is therefore the object of the disclosure to avoid or at least to mitigate the disadvantages of the prior art. In particular, a cost-neutral secondary measure is to be provided for the transmission of higher torques in belt pulley decouplers. 
     This object is achieved according to the disclosure with a generic component in that the connecting flange has a geometry to facilitate a form fit for torque transmission on both the distal face and a proximal face (opposite the distal face), which is intended to come into contact with a torsional vibration damper. 
     This has the advantage that, compared with a simple frictional connection between two components, in particular the hub and the connecting flange, higher torques can be transmitted if these two components are designed in a form-fitting manner by means of the geometry according to the disclosure which facilitates a form fit. 
     Advantageous embodiments are claimed in the dependent claims and are explained below. 
     In a preferred embodiment, the hub can have a geometry on the two end faces thereof to facilitate a torque-transmitting form fit between the crankshaft and the hub on the one hand and the hub and the connecting flange on the other hand. This means that higher torques can also be transmitted between the hub and crankshaft without impairing the operational reliability of the belt pulley decoupler. 
     According to the disclosure, the geometries that facilitate a form fit can be designed in the same way (and in particular identical) on the two end faces of the connecting flange and the hub. The geometry that facilitates a form fit can preferably be designed as a toothing, in particular as an axial toothing, preferably as a Hirth toothing, so that the two components are centered on one another in addition to increasing the transmittable torque. 
     In a further embodiment, the torsional vibration damper can be designed with a geometry that is opposite to the hub facing away from the end face of the connecting flange, to force a connection without play and thus ensure safe operation even at high torques. 
     Preferably, the geometry that facilitates a form fit can be attached by tooling, for example by punching, forging, injection molding, or by machining. For this reason, no further processing steps, in particular cost-intensive secondary measures, are necessary to ensure operational reliability at high torques after the production of the geometry that facilitates a form fit. 
     According to the disclosure, gaps in a toothing can lie approximately or exactly below the tips of the further toothing on the same component, which makes it possible to apply a toothing according to the disclosure on both sides even with very thin components. In other words, according to the disclosure, a component can be designed in such a way that tooth flanks of a first toothing on one end face of the component are essentially parallel and at a constant distance from tooth flanks of a second toothing on the other end face of the component. 
     In a belt pulley decoupler according to the disclosure, forces between components, including the hub, the connecting flange and the torsional vibration damper can be transmitted exclusively or predominantly at the interfaces of the components via a form fit during operation. 
     In a further embodiment, a second torsional vibration damper can be connected in a form-fitting manner by means of a geometry that facilitates a form fit to an end face of the hub facing away from the torsional vibration damper. In this case, the second torsional vibration damper can also have, on the end face thereof facing away from the hub, a shape-locking geometry for connection to the crankshaft. The two geometries of the second torsional vibration damper that facilitate a form fit can preferably be designed as axial toothings in the form of a Hirth toothing, which allows a high torque and at the same time (automatically) ensures centering of the second torsional vibration damper. In other words, in a further embodiment, a second torsional vibration damper can be interposed between the hub and the crankshaft of the internal combustion engine, wherein the connection between the second torsional vibration damper and the hub or the crankshaft is implemented in a form-fitting manner via a Hirth toothing. 
     In other words, the disclosure relates to a proposed double-sided Hirth toothing in a belt pulley decoupler. This toothing is attached on both sides of the connecting flange, the hub and/or on another component and creates form fits between the components. In this way, the torque is positively transmitted through all components. The production of the toothing can be produced by tooling, by punching, forging, injection molding, etc., or also by machining. When producing thin components, e.g., from sheet metal, the toothing can be attached twisted so that the gaps in the rear toothing are exactly below the tips of the front toothing. Another advantage is the additional centering through the Hirth toothing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is explained below with the aid of drawings. In the figures: 
         FIG. 1  shows a schematic arrangement of an auxiliary unit drive known from the prior art of an internal combustion engine having a belt pulley decoupler. 
         FIG. 2  shows a perspective sectional view of a belt pulley decoupler according to a preferred exemplary embodiment. 
         FIG. 3  shows a further sectional view of the belt pulley decoupler according to the preferred exemplary embodiment without torsional vibration damper and screw. 
         FIG. 4  shows yet another sectional view of the belt pulley decoupler according to the preferred exemplary embodiment without a cover and connecting flange. 
         FIGS. 5 and 6  show perspective views of a connecting flange of the belt pulley decoupler according to the preferred exemplary embodiment. 
         FIGS. 7 and 8  show perspective views of a hub of the belt pulley decoupler according to the preferred exemplary embodiment. 
         FIG. 9  shows a perspective sectional view of a belt pulley decoupler according to a modified exemplary embodiment. 
         FIG. 10  shows a perspective sectional view of a second torsional vibration damper of the belt pulley decoupler according to the modified exemplary embodiment. 
     
    
    
     The figures are only schematic in nature and serve only for understanding the disclosure. The same elements are provided with the same reference numbers. The features of the exemplary embodiments can be interchanged. 
     DETAILED DESCRIPTION 
       FIG. 1  schematically shows an arrangement of an auxiliary unit drive  1  of a vehicle having an internal combustion engine  2 . A crankshaft  3  of the internal combustion engine  2  is rotatably coupled to a belt pulley decoupler  4 , which transmits the torque of the internal combustion engine  2  to an endless traction means  5 , e.g., in the form of a belt or a chain, so that auxiliary units  6  are driven when the crankshaft  3  rotates. As auxiliary units  6  can be arranged on the internal combustion engine  2 , for example, an alternator or an electric motor to assist when restarting the internal combustion engine  2  in a start-stop mode, 
       FIG. 2  shows the belt pulley decoupler  4 , which is arranged on the crankshaft  3  of the internal combustion engine  2 . In the preferred exemplary embodiment, the belt pulley decoupler  4  has a hub  7  which is rotatably coupled to the crankshaft  3 , a connecting flange  8  to which a torque introduced from the crankshaft  3  can be transmitted to the hub  2 , and which, with the interposition of at least one bow spring  9 , at least partially transmits introduced torque to a belt pulley body/belt pulley  10 . Furthermore, a torsional vibration damper  11  is arranged on the belt pulley decoupler  4 . As can be seen in  FIG. 2 , the hub  7 , the connecting flange  8 , and the torsional vibration damper  11  are arranged to be coaxial in this order away from the crankshaft  3  and opposed by a screw  12  which engages with an internal thread formed in the crankshaft  3  to clamp/secure the crankshaft  3 . 
     During operation of the internal combustion engine  2 , the hub  7  rotates at a speed specified by the crankshaft  3  and transmits this and the torque of the internal combustion engine  2  to the connecting flange  8 . The connecting flange  8  driven in this way is in turn in torque-transmitting contact with the at least one bow spring  9 , which is coupled to the belt pulley body  10  via corresponding projections  13 . The belt pulley body  10  forms a pulley  14  which is designed to come into contact with the endless traction means  5 . To compensate for rotational irregularities, that is, to increase the smoothness of the belt pulley decoupler  4  and at least partially decouple it from impacts in the crankshaft  3 , the torsional vibration damper  11  is also connected to the hub  7 , as described above. 
     The torque that is generated by combustion in the internal combustion engine  2  can thus be transmitted via the crankshaft  3 , the hub  7 , the connecting flange  8 , and the bow spring  9  to the belt pulley body  10  and finally to the endless traction means  5 . In the preferred exemplary embodiment, the endless traction means  5  serves, as described above, to drive the auxiliary units  6  of the vehicle in which the internal combustion engine  2  is mounted, e.g., such as an alternator or the like. 
     In other words, the torque of the internal combustion engine  2  is along a first power flow path from the crankshaft  3  to the hub  7 , from the hub  7  to the connecting flange  8 , from the connecting flange  8  to the at least one bow spring  9 , and from the bow spring  9  to the belt pulley body  10  and passed on to the auxiliary unit drive/belt drive  1 . The torque of the internal combustion engine  2  for vibration damping is transmitted along a second power flow path from the crankshaft  3  to the hub  7 , from the hub  7  to the connecting flange  8 , and then from the connecting flange  8  to the torsional vibration damper  11 . 
     As can be seen in  FIGS. 3 and 4 , a cover  15  is arranged on the belt pulley body  10  on the torsional vibration damper side. This holds the at least one bow spring  9  in a cavity formed between cover  15  and belt pulley body  10 . In the preferred exemplary embodiment are formed for coupling the connecting flange  8  to the belt pulley body  10  two projections  13  on the latter, between each of which is arranged a bow spring  9 . 
       FIGS. 5 and 6  each show perspective views of the connecting flange  8 . In the preferred exemplary embodiment, the connecting flange  8  has an essentially disk-shaped base body from which two opposing, plate-shaped tongues stick out/protrude in the radial direction. Furthermore, an axial spur toothing (axial toothing) in the form of a Hirth toothing is formed on the base body of the connecting flange  8  both on the torsional vibration damper-side end section/end face thereof and on the hub-side end section/end face thereof, which are each in engagement with a complementary spur toothing on the torsional vibration damper  11  or on the hub  7 , as can be seen in  FIG. 8 . 
     In the preferred exemplary embodiment, the two spur toothings of the connecting flange  8  are designed in such a way that the tooth flanks of the one spur toothing are arranged to be parallel at a constant distance from the tooth flanks of the second spur toothing. Thus, the connecting flange  8  can be designed with a small material thickness without impairing the transmittable torque. 
     In other words, the two spur toothings of the connecting flange  8  are designed to be rotated with respect to one another, so that the tooth gaps of the one toothing are arranged in the axial direction exactly behind the tooth tips of the second toothing. 
     Perspective views of the hub  7  are shown in  FIG. 7  and  FIG. 8 . In the preferred exemplary embodiment, similar to the connecting flange  8 , in addition to the spur toothing which is in engagement with the connecting flange  8 , on the end section/face on the connecting flange side, an axial spur toothing in the form of a Hirth toothing is also formed on the crankshaft-side end section/face on the hub  7  which in turn meshes with a complementary axial spur toothing on the crankshaft  3 . A circumferential projection is formed on a central section of the hub  7 , which as can be seen in  FIG. 2  serves as an axial stop for the belt pulley body  10  in an assembled state of the belt pulley decoupler  4 . 
     The form fit connections between hub  7  and connecting flange  8  and between connecting flange  8  and torsional vibration damper  11 , and between hub  7  and crankshaft  3  ensure safe operation even with higher torques to be transmitted, without needing to provide additional cost-intensive secondary measures. In addition, the crankshaft  3 , the hub  7 , the connecting flange  8 , and the torsional vibration damper  11  are centered with respect to one another via the spur toothings. 
       FIG. 9  shows a perspective sectional view of a belt pulley decoupler  4  according to a modified exemplary embodiment. The structure of the belt pulley decoupler  4  is analogous to the preferred exemplary embodiment. To simplify the illustration, the cover  15 , the screw  12  and the bow spring  9  are omitted in  FIG. 10 . In the belt pulley decoupler  4  according to the modified exemplary embodiment, a second torsional vibration damper  16  is arranged between the hub  7  of the belt pulley decoupler  4  and the crankshaft  3  of the internal combustion engine  2 . As shown in  FIG. 10 , the second torsional vibration damper  16  has an axial spur toothing in the form of a Hirth toothing both on the hub-side end section thereof and on the crankshaft-side end section thereof, each of which are engaged with the spur toothing of the hub  7  or the spur toothing of the crankshaft  3 . 
     A belt pulley decoupler  4  according to a preferred exemplary embodiment is described above. It goes without saying, however, that the description is only exemplary and the scope of protection of the disclosure is defined by the claims. 
     In the preferred exemplary embodiment, the connecting flange  8  is designed with the two mutually opposite tongues. However, only one tongue or a plurality of tongues can be arranged over the circumference of the connecting flange  8 . 
     Furthermore, in the preferred exemplary embodiment, two projections  13  are arranged on the belt pulley body  10 , and two bow springs  9  are used in the belt pulley decoupler  4 . However, only one projection can be formed and a bow spring can be used. Alternatively, a large number of projections can also be formed with bow springs arranged therebetween. 
     LIST OF REFERENCE NUMBERS 
     
         
         
           
               1  Auxiliary unit drive 
               2  Internal combustion engine 
               3  Crankshaft 
               4  Belt pulley decoupler 
               5  Endless traction means 
               6  Auxiliary unit 
               7  Hub 
               8  Connecting flange 
               9  Bow spring 
               10  Belt pulley body 
               11  Torsional vibration damper 
               12  Screw 
               13  Projection 
               14  Belt pulley 
               15  Cover 
               16  Second torsional vibration damper