Patent Publication Number: US-2022221040-A1

Title: Isolated drive assembly with an isolator assembly and a torque limiter for limiting the transmission of torque through an elastomeric element of the isolator assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 63/134,992 filed Jan. 8, 2021, the disclosure of which is incorporated by reference as if fully set forth in detail herein. 
    
    
     FIELD 
     The present disclosure relates to an isolated drive assembly that is configured to transmit power through rotary drive, such as a belt or chain, or through a plurality of meshing teeth. The isolated drive assembly includes an isolator assembly and a torque limiter that is configured to limit the transmission of torque through a resilient element of the isolator assembly. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Modern automotive vehicles that utilize an internal combustion engine to provide propulsive power will typically have a front engine accessory drive (FEAD) that transmits power through a belt from a crankshaft of the internal combustion engine to a plurality of engine accessories, such as a water pump, an air conditioning compressor and an alternator. The FEAD will commonly include a pulley assembly that is mounted on the crankshaft and which is configured to attenuate or soften spikes in the magnitude of the power that is transmitted through the pulley (i.e., between the belt and the engine crankshaft). In general, these spikes are generated by irregularities in the operation of the engine (i.e., the firing of the engine cylinders). 
     One method for attenuating spikes in the transmission of power between the pulley and the belt involves a mechanical decoupler that employs one or more helical compression springs and a clutch to permit decoupling of the crankshaft of the engine from the pulley. These devices are relatively complex and can be relatively heavy. Moreover, the clutching components introduce additional potential failure modes into the FEAD and there may be concerns as to whether the device would “fail safe” so that rotary power would be transmitted between the engine crankshaft and the belt regardless of the manner in which the clutch may fail. 
     Another common technique is to segregate the pulley into a pulley component, which is engagable to the belt of the FEAD, and a hub component, which is rotationally coupled to the engine crankshaft, and to employ an elastomeric spring to rotationally couple the pulley component and the hub component in a manner that provides the ability to store or release torque to attenuate torque spikes. It is fairly common for the elastomeric spring to be formed of an ethylene propylene diene monomer (EPDM) rubber material. While elastomeric springs are an effective means for attenuating spikes in the transmission of power between the pulley and the belt, this configuration is susceptible to improvement. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In one form, the present disclosure provides an isolated drive assembly that includes a drive member, a drive member hub, and an isolator assembly. The drive member is rotatable about a rotational axis and defines a drive member hub aperture. The drive member hub is received in the drive member hub aperture and is rotatable about the rotational axis relative to the drive member. The isolator assembly has an isolator hub, an isolator rim and an elastomeric element. The isolator hub is coupled to the drive member hub for rotation therewith about the rotational axis. The isolator rim is coupled to the drive member for rotation therewith about the rotational axis. The elastomeric element resiliently couples the isolator hub and the isolator rim. One of the drive member and the drive member hub defines a plurality of circumferentially spaced apart teeth. Each of the teeth has first and second tooth faces. The other one of the drive member and the drive member hub defines a plurality of grooves. Each of the grooves is at least partly delimited on their opposite circumferential ends by first and second sidewalls formed on the other one of the drive member and the drive member hub. Each of the teeth is disposed in an associated one of the grooves and is located within the associated one of the grooves at an initial position when no torque is transmitted between the isolator assembly and the drive member. Contact between the first tooth faces of the teeth and the first sidewalls limits rotation of the drive member relative to the drive member hub away from the initial position in a first rotational direction. Contact between the second tooth faces of the teeth and the second sidewalls limits rotation of the drive member relative to the drive member hub away from the initial position in a second rotational direction that is opposite the first rotational direction. 
     In another form, the present disclosure provides an isolated drive assembly that includes a drive member, a drive member hub, an isolator assembly, and a torque limiter. The drive member is rotatable about a rotational axis and has a drive member hub aperture. The drive member hub is received in the drive member hub aperture and is rotatable about the rotational axis relative to the drive member. The isolator assembly has an isolator hub, an isolator rim and a silicone rubber element. The isolator hub is coupled to the drive member hub for rotation therewith about the rotational axis. The isolator rim is coupled to the drive member for rotation therewith about the rotational axis. The silicone rubber element resiliently couples the isolator hub and the isolator rim. The torque limiter has a first limiter element, which is coupled to the drive member for rotation therewith, and a second limiter element that is coupled to the drive member hub for rotation therewith. Relative rotation between the drive member and the drive member hub in a first rotational direction in response to transmission of a moment between the drive member and the drive member hub in the first rotational direction that is greater than or equal to a first predetermined magnitude is limited by contact between a first portion of the first limiter element and a first portion of the second limiter element when a first moment is transmitted. Relative rotation between the drive member and the drive member hub in a second, opposite rotational direction in response to transmission of a moment between the drive member and the drive member hub in the second rotational direction that is greater than or equal to a second predetermined magnitude is limited by contact between a second portion of the first limiter element and a second portion of the second limiter element. The first and second limiter elements are not in contact with one another when rotary power is not transmitted through the silicone rubber element. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a schematic illustration of an exemplary isolated drive assembly constructed in accordance with the teachings of the present disclosure, the isolated drive assembly being shown in the environment of a front engine accessory drive that is powered by an internal combustion engine; 
         FIG. 2  is a front view of the isolated drive assembly of  FIG. 1 ; 
         FIG. 3  is a section view taken along the line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is an exploded perspective view of the isolated drive assembly of  FIG. 1 ; and 
         FIG. 5  is a section view taken along the line  5 - 5  of  FIG. 3 . 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 and 2  of the drawings, an exemplary isolated drive assembly constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The isolated drive assembly  10  is schematically illustrated in  FIG. 1  in operative association with a front engine accessory drive (FEAD)  12  that is powered by an internal combustion engine  14 . The FEAD  12  further includes a drive belt  20  and a plurality of pulleys  22  that can be associated with various engine accessories (e.g., a water pump  24 , a power steering pump  26 , an air conditioning compressor  28 , and an alternator  30 ), an idler pulley  32 , and/or a pulley  34  of a belt tensioner  36 . The isolated drive assembly  10 , which is rotatably coupled to a crankshaft  16  of the internal combustion engine  14  to receive power therefrom, transmits power between the crankshaft  40  and the pulleys  22  of the various engine accessories. 
     The isolated drive assembly  10  is configured to attenuate the fluctuations in torque that are produced by the internal combustion engine  14  during its operation and which would otherwise be transmitted through the crankshaft  40  to the FEAD  12  in an instantaneous manner if a conventional (solid) pulley were to be employed in the FEAD  12  instead of the isolated drive assembly  10 . As such, it will be appreciated that the isolated drive assembly  10  is configured to provide some isolation of the accessories that are driven by the FEAD  12  from torsional fluctuations caused by the operation of the internal combustion engine  14  and that the isolated drive assembly  10  is a type of torsional isolator. Moreover, because the isolated drive assembly  10  attenuates the transmission of torque spikes from the crankshaft  14  to the accessories that are driven by the FEAD  12 , the isolated drive assembly  10  is a type of torque filter that is that is similar to a “low pass filter”. 
     It will be appreciated that while the isolated drive assembly  10  is illustrated and described as being configured for use in a system between a shaft (i.e., the crankshaft  40 ) and a drive belt  20 , the teachings of the present disclosure have broader application. In this regard, an isolated drive assembly constructed with the teachings of the present disclosure could be employed to transmit power in a system where power is transmitted between a sprocket and a chain, in a system where power is transmitted between meshing gears, or in a system where power is transmitted between shafts, for example. 
     With reference to  FIGS. 3 and 4 , the isolated drive assembly  10  can include a drive member  50 , a drive member hub  52 , an isolator assembly  54  and a torque limiter  56 . In the example provided, the isolated drive assembly  10  further includes a torsional vibration damper  58  and a seal flange  60 , both of which are optional. 
     The drive member  50  is configured as the output of the isolated drive assembly  10  in the example provided, but it will be appreciated that an isolated drive assembly  10  constructed in accordance with the teachings of the present disclosure could employ the drive member  50  as the input to the isolated drive assembly  10 . In the example shown, the drive member  50  has a drive element  70 , an inner drive member wall  72 , and a support wall  74 . The drive element  70  extends circumferentially about a rotational axis  80  and has a first outer circumferential surface  82  and a first inner circumferential surface  84 . As the drive element  70  is a pulley sheave, the first outer circumferential surface  82  can be configured to engage the drive belt  20 . The inner drive member wall  72  can extend circumferentially about the rotational axis  80  concentric with the drive element  70 . The inner drive member wall  72  can have a second outer circumferential surface  92  and a second inner circumferential surface  94 . The second inner circumferential surface  94  can define a drive member hub aperture  96 . The support wall  74  can extending radially between and can rotationally couple the drive element  70  and the inner drive member wall  72 . Accordingly, the drive element  70  can be formed as an annular channel where the drive element  70  and the inner drive member wall  72  are concentric walls that are spaced apart from and coupled to one another by the support wall  74 . 
     The drive member hub  52  is configured to be coupled to the crankshaft  40  for rotation therewith. The drive member hub  52  can have a cup-like shape with an annular hub wall  100  and a hub end wall  102 . The annular hub wall  100  is sized to be received into the drive member hub aperture  96  in the drive member  50  so that the drive member  50  is rotatable about the rotational axis  80  relative to the drive member hub  52 . If desired, a seal can be disposed between the drive member hub  52  and the drive member  50 . In the example provided, the annular hub wall  100  defines a seal groove  106  into which a seal  108  is received. The seal  108  sealingly engages an exterior circumferential surface of the annular hub wall  100  and the second inner circumferential surface  94  on the inner drive member wall  72 . The hub end wall  102  can span radially across an axial end of the annular hub wall  100 . One or more fastener apertures  110  can be formed through the hub end wall  102  and associated threaded fasteners  112  can be received through the fastener apertures  110  to secure the drive member hub  52  to the crankshaft  40 . 
     The isolator assembly  54  can have an isolator hub  120 , an isolator rim  122  and an elastomeric element  124 . The isolator hub  120  is coupled to the drive member hub  52  for rotation therewith about the rotational axis  80 . The isolator rim  122  is coupled to the drive member  50  for rotation therewith about the rotational axis  80 . The elastomeric element  124  resiliently couples the isolator hub  120  and the isolator rim  122 . The elastomeric element  124  can be formed of any desired elastomer, such as ethylene propylene diene monomer (EDPM) rubber. However, silicone rubber is the presently preferred material for the elastomeric element  124 . 
     In the specific example provided, the isolator hub  120  includes a hub portion  130 , which spans across the inner drive member wall  72  of the drive element  70 , an isolator mount  132 , which has a tubular shape that extends axially along the rotational axis  80  from a radially outer end of the hub portion  130 , and a flange member  134  that extends radially outwardly from the isolator mount  132  on an axial end of the isolator mount  132  that is opposite the hub portion  130 . A plurality of fastener apertures  136  are formed through the hub portion  130  and are aligned to the fastener apertures  110  formed in the drive member hub  52 . The isolator rim  122  is a tubular segment. The elastomeric element  124  is bonded to the exterior circumferential surface of the isolator mount  132  and to the interior circumferential surface of the isolator rim  122 . The exterior circumferential surface of the isolator rim  122  can be fixedly coupled to the first inner circumferential surface  84  of the drive element  70 , for example via press-fitting. With the configuration shown, a portion of the isolator assembly  54  that includes the elastomeric element  124  is disposed in the annular channel that is formed by the drive element  70 . 
     A bearing  140  can be disposed between the drive member  50  and the isolator hub  120 . In the example shown, the bearing  140  comprises a tubular bearing portion  142 , which is received onto the second outer circumferential surface  92  of the inner drive member wall  72  as well as the inner circumferential surface of the isolator mount  132 , and a bearing flange  144  that is disposed axially between the support wall  74  on the drive member  50  and the flange member  134  on the isolator hub  120 . 
     It will be appreciated that the isolator assembly  54  could be configured somewhat differently and could be connected to the drive element  70  in a different manner. For example, the isolator assembly  54  could be configured so that the isolator rim  122  is disposed radially inwardly of the isolator mount  132 , the isolator rim  122  is fixedly mounted to the inner drive member wall  72  and the tubular bearing portion  142  of the bearing  140  engages the first inner circumferential surface  84  on the drive element  70 . 
     The torque limiter  56  is configured to limit relative rotation between the drive member  50  and the drive member hub  52  in a first rotational direction to prevent the elastomeric element  124  from being subjected to a torque that is directed in the first rotational direction and which exceeds a first predetermined magnitude, and to limit relative rotation between the drive member  50  and the drive member hub  52  in a second rotational direction that is opposite the first rotational direction to prevent the elastomeric element  124  from being subjected to a moment that is directed in the second rotational direction and which exceeds a second predetermined magnitude. The torque limiter  56  is preferably disposed in a chamber that is protected from dirt and debris. In the example provided, the torque limiter  56  is disposed in a chamber that is delimited by the bearing  140 , the isolator hub  124 , the drive member hub  52 , the seal  108 , and the inner drive member wall  72  of the drive member  50 . 
     With reference to  FIGS. 3 and 5 , the torque limiter  56  can include one or more teeth  150 , which can be coupled for rotation with one of the drive member  50  and the drive member hub  52 , and a corresponding set of drive elements  152 , that can be coupled to the other one of the drive member  50  and the drive member hub  52 . In the example provided, the teeth  150  are coupled for rotation with the drive member  50  and extend radially inwardly from the inner drive member wall  72 . Each of the teeth  150  has a first tooth face  154  and a second tooth face  156 . The drive member hub  52  defines a plurality of groove  160 , which are formed into the annular hub wall  100  and which can define the drive elements  152 . Each of the groove  160  has first and second sidewalls  164  and  166 , respectively, that are spaced circumferentially apart from one another. The first and second sidewalls  164  and  166  comprise the set of drive elements that are rotatably coupled to the drive member hub  52 . Each of the teeth  150  is received into an associated one of the grooves  160 . Rotation of the drive member  50  about the rotational axis  80  relative to the drive member hub  52  in the first rotational direction is limited by contact between the first tooth faces  154  and the first sidewalls  164 , while rotation of the drive member  50  about the rotational axis  80  in the second rotational direction is limited by contact between the second tooth faces  156  and the second sidewalls  166 . 
     Returning to  FIGS. 3 and 4 , the torsional vibration damper  58  can be configured to damp vibration at a predetermined frequency that is generated by the internal combustion engine  14  ( FIG. 1 ) during its operation. The torsional vibration damper  58  can be any type of torsional vibration damper, such as a viscous damper or a tuned rubber damper that employs one or more springs and an inertia ring. In the particular example provided, the torsional vibration damper  58  is a conventional viscous damper with a damper hub  170  having fastener apertures  172  formed therethrough and which are aligned to the fastener apertures  110  and  136  formed in the drive member hub  52  and the hub portion  130  of the isolator hub  120 . 
     The seal flange  60  can be configured to adapt the drive member hub  52 , the isolator hub  120 , and if included, the damper hub  170  of the torsional vibration damper  58  to the crankshaft  40  in a manner that positions the drive member  50  at a desired location along the rotational axis  80  relative to the pulleys  22  ( FIG. 1 ) of the FEAD  12  ( FIG. 1 ), as well as maintains the rotational axis  80  coincident with a rotary axis of the crankshaft  40 . The seal flange  60  can include a crankshaft pilot portion  180 , which is formed in a first axial end of the seal flange  60  and which is configured to pilot onto a portion of the crankshaft  40  to align the rotational axes of the seal flange  60  and the crankshaft  40  to one another, and a cylindrical projection  182  that extends from a second, opposite axial end of the seal flange and which is configured to be received into through-holes formed through the drive member hub  52 , the isolator hub  120  and the damper hub  170  as shown in  FIG. 3  to align the rotational axis  80  to the rotational axis of the seal flange  60 . The cylindrical projection  182  can be sized to provide a light press-fit with the through-hole formed in the drive member hub  52  so that engagement of the cylindrical projection  182  to the drive member hub  52  axially retains the components of the isolated drive assembly  10  to one another prior to the installation of the isolated drive assembly  10  to the crankshaft  40 . A plurality of fastener apertures  186  can be formed axially through the seal flange  60 . The threaded fasteners  112  can be received through the fastener apertures  110 ,  136 ,  172  and  186  in the drive member hub  52 , the isolator hub  120 , the damper hub  170 , and the seal flange  60  and threaded into corresponding threaded holes  188  in the crankshaft  40  to fixedly couple the isolated drive assembly  10  to the crankshaft  40 . Optionally, a washer  190  can be disposed between the heads  192  of the threaded fasteners  112  and the hub end wall  102  of the drive member hub  52 . Also optionally, the seal flange  60  may also include a circumferentially extending seal surface  196  that is configured to be engaged by a dynamic seal (not shown) that is housed in a component of the internal combustion engine  14  ( FIG. 1 ). The dynamic seal may be mounted to a front cover (not shown) of the internal combustion engine  14  ( FIG. 1 ) and can include one or more seal lips (not shown) that can be sealingly engaged to the circumferentially extending seal surface  196 . 
     With reference to  FIGS. 3 and 5 , the torque limiter  56  is disposed in an initial position (shown in  FIG. 5 ) when no power is transmitted through the isolated drive assembly  10 . In the initial position, the first tooth face  154  is spaced from the first sidewall  164  by a first angle  200 , and the second tooth face  156  is spaced from the second sidewall  166  by a second angle  202 . 
     When the internal combustion engine  14  ( FIG. 1 ) is operated to drive the drive belt  20  of the FEAD  12  ( FIG. 1 ), the angular spacing between the first tooth face  154  and the first sidewall  164  will diminish as more torque is required to drive the accessories. In situations where the load created by the accessories is relatively high and the load on one or more of the accessories increases suddenly, for example through the switching on of an air conditioning compressor or the placement of a sudden demand for high current electrical power on the alternator, the torque required to drive the accessories may be equal to a first predetermined threshold. In such situations, a first set of engageable torque limiter elements can engage one another to limit rotation of the drive member  50  relative to the drive member hub  52  in the first rotational direction to prevent the elastomeric element  124  from being subjected to a first moment that is directed in the first rotational direction and which exceeds a first predetermined magnitude. In this regard, the amount of torque that is needed to drive the accessories that exceeds the magnitude of the first moment is transmitted from the drive member  50  through the first set of engageable torque limiter elements (i.e., the first tooth face  154  and the first sidewall  164  in the example provided) to the drive member hub  52 . 
     At times during the operation of the internal combustion engine  14  ( FIG. 1 ) and the FEAD  12  ( FIG. 1 ), there will be times where the rotational inertia of one or more of the accessories will tend to drive the drive belt  20  of the FEAD  12  ( FIG. 1 ) so that load is effectively removed from the drive member  50  and the elastomeric element  124 . In such situations, the angular spacing between the first tooth face  154  and the first sidewall  164  will decrease as less torque is required to drive the accessories. In some cases, the rotational inertia of the high-rotational inertia accessory or accessories is sufficient to drive the drive member  50  in the second rotational direction relative to the drive member hub  52  away from the initial position (i.e., the position where no moment is transmitted through the elastomeric element  124 ) so that the angular spacing between the second tooth face  156  and the second sidewall  166  decreases. 
     A second set of torque limiter elements can engage one another to limit the transmission of power through the elastomeric element  124  in the second rotational direction in situations where one or more of the accessories would tend to back-drive the crankshaft  40 . In such situations, a second set of engageable torque limiter elements can engage one another to limit rotation of the drive member  50  relative to the drive member hub  52  in the second rotational direction to prevent the elastomeric element  124  from being subjected to a second moment that is directed in the second rotational direction and which exceeds a second predetermined magnitude. In this regard, the amount of torque that is applied to the drive member  50  through the drive belt  20  from the accessories that exceeds the magnitude of the second moment is transmitted from the drive member  50  through the second set of engageable torque limiter elements (i.e., the second tooth face  156  and the second sidewall  166  in the example provided) to the drive member hub  52 . 
     It will be appreciated that the magnitudes of the first and second moments can be set to desired levels and that the two magnitudes need not be equal. For example, the magnitude of the first moment can be larger than the magnitude of the second moment. As such, the magnitude of the first angle  200  can be larger than the magnitude of the second angle  202 . Preferably, the magnitude of the first angle  200  is about 1.5 to 2.5 times the magnitude of the second angle  202 . More preferably, the magnitude of the first angle  200  is about twice as large as the magnitude of the second angle  202 . In the example provided, the first angle  200  has a magnitude of about 40 degrees and the second angle  202  has a magnitude of about 20 degrees. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.