Patent Publication Number: US-2022213954-A1

Title: Decoupler

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Phase of PCT Appln. No. PCT/DE2020/100394 filed May 11, 2020, which claims priority to DE 10 2019 112 738.6 filed May 15, 2019, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a decoupler for the drive torque transmission between the belt of an auxiliary unit belt drive and the shaft of one of the auxiliary units. 
     BACKGROUND 
     Torsional vibrations and irregularities that are introduced from the crankshaft of an internal combustion engine into the belt drive of the auxiliary units can, as is known, be compensated for by decouplers, which are also referred to as isolators and are typically designed as generator belt pulleys. The vibration compensation is provided by the torsion spring, which allows (elastic) relative rotations of the belt pulley with respect to the hub when the drive torque is transmitted. 
     In order to dampen vibrations of these relative rotations, a decoupler with a torsional vibration damper is known from the generic WO 2016/037283 A1, the damping friction force of which increases with the drive torque transmitted by the torsion spring. The torsional vibration damper is designed in such a way that a plain bearing ring that rotates the belt pulley on the hub absorbs the force component of the drive torque transmitted from the spring end on the hub side to the rotary stop there. The plain bearing ring is guided to the hub in a radially movable manner in the direction of this drive force and transfers the drive force as a friction contact force from its (hub-side) friction contact surface to a friction contact surface that is non-rotatable with the belt pulley. 
     SUMMARY 
     It is desirable to specify a decoupler of the type mentioned at the outset with an alternatively designed torsional vibration damper. 
     Accordingly, the first friction contact surface should be part of a pressure piece, that moves radially in relation to the first spring plate and which absorbs the drive force introduced by the rotary stop of the first spring plate into the spring end in contact with a catch and transmits it to the hub via the contact force of the friction contact surfaces. Thus, the drive torque-dependent torsional vibration damping of the decoupler is provided by a mechanism which picks up the driving force on the part of the first spring plate and not—as is the case in the cited prior art—the driving force on the part of the second spring plate and transmits it as a friction contact force to the contact partner rotating relative thereto. 
     This structural positioning of the torsional vibration damper makes it possible in particular to leave the plain bearing between the belt pulley and the hub, which is typically arranged in the area of the second spring plate, unchanged and to supplement its friction damping with the additional torsional vibration damping in the area of the first spring plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features emerge from the following description and from the drawings, in which an exemplary embodiment of a decoupler for the generator arranged in the auxiliary belt drive of an internal combustion engine is shown. In the figures: 
         FIG. 1  is the belt pulley decoupler in a longitudinal section; 
         FIG. 2  is the auxiliary belt drive with the decoupler in a schematic representation; 
         FIG. 3  is the decoupler in an exploded view; 
         FIG. 4  is the section I-I according to  FIG. 1 ; 
         FIG. 5  is the pressure piece according to  FIGS. 1, 3 and 4  as an individual part in perspective; 
         FIG. 6  is the first spring plate according to  FIGS. 1, 3 and 4  as an individual part in perspective. 
     
    
    
     DETAILED DESCRIPTION 
     The decoupler  1  shown in detail in  FIGS. 1 and 3  is arranged on the generator  2  of the auxiliary unit belt drive of an internal combustion engine shown schematically in  FIG. 2 . The belt  4  driven by the belt pulley  3  of the crankshaft loops around the belt pulley  5  of the decoupler  1 , the belt pulley  6  of an air conditioning compressor and a deflection belt pulley  7 . The belt  4  is pretensioned by means of a belt tensioner  8 . 
     The belt pulley  5  rotating in the direction of the arrow shown in  FIG. 3  is hollow-cylindrical, and its outer jacket, wrapped around by the belt  4 , is profiled in accordance with the poly-V shape of the belt  4 . The belt pulley  5  is rotatably mounted on a hub  9  which is screwed firmly to the generator shaft in a known manner. The belt pulley  5  is supported on the hub  9  at the generator-side end radially and axially by means of a deep groove ball bearing  10  and at the end remote from the generator radially by means of a plain bearing ring  11  made of polyamide. After the decoupler  1  has been mounted on the generator  2 , a protective cap  12  is snapped onto the end of the belt pulley  5  remote from the generator, which protects the interior of the decoupler  1  from dirt and splash water. 
     The essential component for the function of the decoupler  1  is a torsion spring  13 , which, due to its elasticity, transfers the drive torque of the belt  4  from the belt pulley  5  to the hub  9  in a decoupling manner, so that the torsional vibrations of the crankshaft are only transferred to the generator shaft to a significantly reduced extent. A loop belt coupling  14  connected in series with the torsion spring  13  causes the drive torque—neglecting the internal drag torque of the opened loop belt coupling  14 —to be only transferred from the belt  4  to the generator shaft (and not the other way around, as is the case with alternative versions of the decouplers without freewheeling function). The torsion spring  13  and the looped belt coupling  14  each extend coaxially to the axis of rotation  15  of the decoupler  1 , wherein the looped belt coupling  14  runs in the radial annular space between the belt pulley  5  and the torsion spring  13 . 
     Both the right-wound loop belt coupling  14  and the left-wound torsion spring  13  are completely cylindrical and have legless ends on both sides which radially expand the looped belt coupling  14  and the torsion spring  13  when the drive torque is transmitted. The loop strap end  16  running in the drive torque flow on the part of the belt pulley  5  is braced against the cylindrical inner jacket  17  of a sleeve  18  which is rotatably secured in the belt pulley  5  and, in the present case, is pressed into place. The loop strap end  19  running in the drive torque flow from the torsion spring  13  is braced against the cylindrical inner jacket  20  of a further sleeve  21 , which is rotatable in the belt pulley  5  and in the present case also in the sleeve  18 . 
     When the looped belt coupling  14  is closed, the drive torque is transmitted by means of static friction between the then radially expanded looped belt coupling  14  and the sleeves  18  and  21  to a first spring plate  22 , which is connected to the sleeve  21  in a non-rotatable manner. In the present case, the first spring plate  22  and the sleeve  21  are formed by a single piece shaped sheet metal part. 
     The loop belt coupling  14  enables the (inertial) generator shaft and the hub  9  secured thereon to be overtaken with respect to the belt pulley  5  when the drive torque is reversed. In this open state, the loop belt coupling  14  contracts to its (unloaded) starting diameter and slips through one or both sleeves  18 ,  21 , wherein the transferable drive torque is reduced to the drag torque between the two slipping contact partners. 
     The torsion spring  13  is clamped with axial pretension between the first spring plate  22 , which is arranged in the drive torque flow on the part of the belt pulley  5 , and a second spring plate  23 , which is arranged in the drive torque flow on the part of the hub  9  and forms an integral part of the hub  9  here. The spring plates  22 ,  23  each have a rotary stop  25  against which the peripheral end faces  26  of the spring ends  27  rest—and as shown in  FIG. 4 —introduce the force component of the drive torque M, i.e., the drive force F into the torsion spring  13 , radially widening in the process. 
     The decoupler  1  is equipped with a torsional vibration damper which dampens the relative torsional vibrations of the belt pulley  5  with respect to the hub  9  by means of Coulomb friction and is explained below with reference to  FIGS. 4 to 6 . The torsional vibration damper has a first friction contact surface  28  which is arranged in the drive torque flow from the belt pulley  5 , and a second friction contact surface  29  which is arranged in the drive torque flow from the hub  9 . The friction between the friction contact surfaces  28 ,  29  that rotate relative to one another and consequently the level of damping of the torsional vibration damper depend on the drive force F introduced into the torsion spring  13  and in the present case are substantially proportional to it and consequently proportional to the transmitted drive torque M of the decoupler  1 . 
     A structurally essential component of the torsional vibration damper is a pressure piece  30  which is arranged on the rear side of the first spring plate  22  and which is non-rotatable with respect to the first spring plate  22  but can be moved radially in the direction of the drive force F. In the present case, the pressure piece  30  is designed as an axial bearing disk that transmits the axial pretensioning force of the torsion spring  13  from the first spring plate  22  to the inner ring of the deep groove ball bearing  10 . The first friction contact surface  28  is part of the pressure piece  30 , and the second friction contact surface  29  is formed by the outer jacket surface  31  of the hub  9  that rotates relative to the first spring plate  22  with the pressure piece  30 . 
     The pressure piece  30  absorbs the drive force F introduced by the rotary stop  25  of the first spring plate  22  into the spring end  27  in contact with a catch  32  and transmits the drive force F as mutual contact force F of the friction contact surfaces  28 ,  29  to the hub  9 . The friction force FR corresponding to the contact force F causes the vibration damping proportional to the drive force F and the drive torque M. 
     The first friction contact surface  28  and the catch  32  are formed on a protrusion  33  or by a protrusion  34  on the axial bearing disk, wherein the protrusions  33 ,  34  engage recesses  35  and  36  therein to produce torsional rigidity and radial mobility relative to the first spring plate  22 . The protrusion  33 ,  34  and the recesses  35 ,  36  each have the shape of an annular passage, wherein the rotary stop  25  of the first spring plate  22  is spaced 90° from the annular piece centers of the protrusions  33 ,  34 . 
     The pressure piece  30  is a plastic part made of PEEK or PA46 with metallic reinforcement  37 , wherein the first friction contact surface  28  and the spring receptacle  38  of the catch  32  contacting the spring end  27  is made of PEEK or PA46.