Abstract:
An idler pulley is described for a front end accessory drive. The idler pulley includes plurality of angled spokes, such as angled ribs molded into the pulley to join an outer hub and an outermost belt interacting region. As the belt runs over the surface of the pulley, any defects on the belt running surface of the pulley due to shrinkage and fill are now angled, and angling of the defects reduces direct impact with the belt and therefore reduces the structureborne noise produced by operation of the belt and the pulley.

Description:
FIELD 
       [0001]    The present application relates to a pulley with NVH reducing features in a serpentine belt drive system for a vehicle. 
       BACKGROUND AND SUMMARY 
       [0002]    Various engine systems may use pulleys, such as the engine front end accessory drive (FEAD). In one example, the FEAD includes a serpentine belt system driving a plurality of peripheral devices, such as an alternator, power steering pump, water pump, A/C compressor, air pump, etc. Further, the belt may also be guided by an idler pulley and/or a belt tensioner (which may be spring loaded, hydraulic, or manual). In some examples, the pulley wheel is attached to an axle via spokes which are extended from the axle to the wheel, where the spokes intersect with the wheel as structural ribs traversing straight across the width of the wheel and perpendicular to the sides of the wheel. 
         [0003]    A pulley, such as a nylon backside idler may emit a structure-borne noise corresponding the frequency and number of structural ribs when used in an automotive FEAD or other serpentine belt drive system application. The perpendicular structural ribs result in a harmonic defect on the belt running surface of the idler pulley due to material shrinkage and mold fill abnormalities. The defects on the surface of the pulley can impact the belt as it passes over the outer surface of the idler pulley, resulting in the structure-borne noise audible to the user. 
         [0004]    In one approach, described in U.S. Pat. No. 6,648,784, an idler sprocket/pulley includes teeth, complementary to teeth of a belt in the belt drive system. The teeth of the sprocket/pulley have an arcuate pitch that substantially matches the pitch of a belt when engaged with the sprocket/pulley at the mating interface, thus accounting for the wrap angle of the belt and reducing noise generated during operation of the belt system due to reduced contact between a sprocket tooth and a belt land. 
         [0005]    The inventors herein recognize potential issues with such an idler pulley design. As one example, in the previously described pulley, the pulley only provides noise reduction when used in combination with a specific belt. The pitch of the belt must precisely match that of the pulley in order to function in noise reduction. If a replacement belt is provided without the specific matching pitch, noise may be significantly increased. 
         [0006]    In another example, the belt used in combination with the previously described pulley may stretch or warp as it ages. As the belt ages, the teeth of the belt may no longer precisely match the teeth of the pulley, again resulting in increased noise generation during vehicle operation. 
         [0007]    Some of the above issues may be at least partly addressed by a belt drive system for a vehicle, comprising: a front end accessory drive including a plurality of accessory pulleys and an idler pulley rotatably coupled via a continuous belt, the idler pulley comprising, a hub which rotates around a rotational axis; a belt contacting surface on an outermost circular portion; and a plurality of angled spokes connecting the hub and the outermost circular portion. 
         [0008]    In this example, the idler pulley may include angled ribs molded into the pulley to join the hub and an outermost circular portion. As the belt runs over the surface of the pulley, any defects on the belt running surface of the pulley due to shrinkage and fill are now angled. Angling of the defects reduces direct impact with the belt and therefore reduces the structureborne noise produced by operation of the belt and the pulley. The pulley may further include a smooth belt contacting surface, such that the pulley may be used with a belt with a variety of teeth pitches or a belt that substantially lacks teeth. Thus the pulley may provide noise reduction even as the belt ages and/or if the belt is replaced with a one of a differing tooth pitch. 
         [0009]    In one specific example, an idler pulley includes a hub which is rotatably attached to a rotational axis of a FEAD of a vehicle. A belt contacting surface of the pulley may be smooth or include teeth, and spokes connecting the hub to the surface of the pulley may be angled relative to the sides of the pulley (non-perpendicular and non-parallel). A cross section of adjacent spokes yields a series of continuous peaks and valleys having an equal angle between each adjacent ribs and the height of the peaks and valleys is equal to the width of the belt contacting surface. As the spokes are continuous, the pulley may have greater material strength than a pulley with discontinuous spokes. 
         [0010]    The angle between each of the adjacent spokes may range from 5° to 100°. The pulley may be used in combination with a belt with a variety of teeth pitches or a belt that substantially lacks teeth. The pulleys may also retain noise reducing capabilities even as a belt stretches or sustains defects over time and/or if the belt is replaced with one of a differing tooth pitch. 
         [0011]    It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  includes an example embodiment of a front end accessory drive for a vehicle. 
           [0013]      FIG. 2  includes an example embodiment of an idler pulley with angled spokes from the front end accessory drive of  FIG. 1 . 
           [0014]      FIG. 3  includes the idler pulley of  FIG. 2  wherein a section of an outermost circular portion is cutaway to reveal the conformation of the spokes. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The following description relates to serpentine belt drive system for a front end accessory drive (FEAD) of a vehicle, such as a passenger vehicle, configured to power a variety of peripheral vehicle components, including but not limited to a water pump, a power steering pump, an air conditioner, and an alternator. An example embodiment of such a FEAD system is shown in  FIG. 1 . 
         [0016]    In this embodiment, each of a plurality of pulleys is rotatably attached to one of a plurality of rotational axes on in an FEAD on a front of an engine for a vehicle. The plurality of pulleys are rotatably coupled via a continuous drive belt, such that the rotation of a crankshaft pulley drives rotation of all other pulleys. The rotational axis of a pulley may be coupled to a peripheral vehicle component, such as one of those listed above, and may provide power to operate the peripheral vehicle component. 
         [0017]    The plurality of pulleys in the FEAD may include a water pump pulley, a power steering pump pulley, a crankshaft pulley, and an air conditioning compressor pulley, a belt tensioner pulley, and an idler pulley. As stated above, the rotation of the crankshaft pulley may drive rotation of the other pulleys in the system. The rotational axis of the crankshaft pulley may be coupled to the engine, and the engine may rotate the rotational axis to provide power to the crankshaft pulley. Rotation of the crankshaft pulley moves the drive belt across its surface, and in turn movement of the belt may rotate the other pulleys. 
         [0018]    The drive belt may be guided by the idler pulley and/or belt tensioner. The rotational axes of the idler pulley and the belt tensioner are not coupled to peripheral vehicle components and do not provide power/torque to peripheral vehicle components. Instead, the belt tensioner includes an internal pre-set spring and provides tension for the continuous belt and the idler pulley may be used to affect a direction of rotation and spacing rotational axes. The idler pulley may be placed between two pulleys to change the direction of rotation and/or the spacing. The idler pulley rotates in the opposite direction of the preceding driving pulley, and the following pulley rotates in the opposite direction of the idler pulley, the same direction of the preceding driving pulley. 
         [0019]    An example embodiment of an idler pulley drawn to scale is shown in  FIGS. 2 and 3 . In this example embodiment, an idler pulley includes a hub, which rotates around and is fixed to a rotational axis, a belt contacting surface on an outermost circular portion, and a plurality of angled spokes connecting the hub and the outermost circular portion. Such a conformation for an idler pulley may be advantageous in that structureborne noise corresponding to the number and frequency of spokes may be reduced because the spokes intersect the outermost circular portion at an angle. As such, defects on the belt contacting surface of the pulley due to shrinkage and fill during molding are also angled, and will impact the belt at an angle during operation of the FEAD, thereby reducing noise. 
         [0020]    Further, other advantages may include that the idler pulley may retain its noise reducing features even as the belt ages, because it does not rely on a specific spacing or pitch of teeth in the belt. Additionally, the belt may be replaced with a generic belt or a belt that substantially lacks teeth and the idler pulley may still provide noise reduction. For example, as a belt ages is may stretch and lose a specific spacing or pitch of the teeth on the belt. In this example, if the idler pulley relied on a specific pitch or spacing of teeth on the belt it may no longer provide noise reduction. However, as the idler pulley may have a smooth belt contacting surface and angled spokes, the idler pulley may provide noise reduction even if a drive belt has stretched or been replaced with a belt with different pitch or spacing of teeth. 
         [0021]      FIG. 1  shows a front end accessory drive (FEAD)  10  for a vehicle including a plurality of pulleys  40 . Plurality of pulleys  40  includes water pump pulley  12 , power steering pump pulley  14 , crankshaft pulley  16 , alternator pulley  18 , first idler pulley  20 , air conditioning (A/C) compressor pulley  22 , drive belt tensioner  24 , and second idler pulley  26 . Accordingly, water pump pulley  12  may provide power to a water pump (not shown); power steering pump pulley  14  may provide power to a power steering pump (not shown); crankshaft pulley  16  may receive power from a crankshaft (not shown); and, A/C compressor pulley  22  may provide power to an air conditioning unit (not shown). In alternate embodiments, more or fewer pulleys may be included in plurality of pulleys  40  to provide power peripheral vehicle components. Additionally, alternate embodiments may include more than one idler pulley. 
         [0022]    Each of the plurality of pulleys  40  are coupled to engine  30  via one of a plurality of rotational axes  50 . Specifically, water pump pulley  12  is coupled to rotational axis  42 ; power steering pump pulley  14  is coupled to rotational axis  44 ; crankshaft pulley  16  is coupled to rotational axis  46 ; alternator pulley  18  is coupled to rotational axis  48 ; first idler pulley  20  is coupled to rotational axis  52 ; air conditioning (A/C) compressor pulley  22  is coupled to rotational axis  54 ; drive belt tensioner  24  is coupled to rotational axis  56 ; and, second idler pulley  26  is coupled to rotational axis  58 . 
         [0023]    Plurality of pulleys  40  are rotatably coupled via drive belt  28 . In  FIG. 1 , drive belt  28  is shown as a single continuous serpentine belt. In alternate embodiments, the pulleys may be coupled via multiple V-belts. Counterclockwise rotation of rotational axis  46  may be powered by engine  30 . Crankshaft pulley  16  is fixed to rotational axis  46  and may rotate with rotational axis  46 . As the outer edge of crankshaft pulley  16  moves, the drive belt  28  may contact the outer edge and move at the same rate. 
         [0024]    Concurrently, movement of drive belt  28  by the crankshaft pulley  16  may drive rotation of the other pulleys. Specifically, drive belt tensioner  24  may rotate counterclockwise; A/C compressor pulley  22  may rotate counterclockwise; second idler pulley  26  may rotate clockwise; first idler pulley  20  may rotate clockwise; crankshaft pulley  16  may rotate counterclockwise; power steering pump pulley  14  may rotate clockwise; and, water pump pulley  12  may rotate clockwise. In an alternate embodiment, the crankshaft pulley may rotate counter clockwise, and thus reverse the rotation of all other pulleys. Rotation of pulleys coupled to peripheral vehicle components may provide power to operate the peripheral vehicle components. 
         [0025]    As shown in  FIG. 1 , first idler pulley  20  is disposed between and above A/C compressor pulley  22  and crankshaft pulley  16 . Drive belt  28  extends downward from belt tensioner  24  and wraps around approximately ⅔ of A/C compressor pulley  22 . 
         [0026]    Movement of drive belt  28  may rotate A/C compressor pulley  22  in a counterclockwise direction during operation of the vehicle. Drive belt  28  extends upward from A/C compressor pulley  22  to first idler pulley  20  and wraps around approximately ½ of first idler pulley  20 . Movement of drive belt  28  may rotate first idler pulley  20  in a clockwise direction during operation of the vehicle. Drive belt  28  again extends downward between first idler pulley  20  and crankshaft pulley  16  and wraps around approximately ½ of crankshaft pulley  16 . Movement of drive belt  28  may rotate crankshaft pulley  16  in a counterclockwise direction during operation of the vehicle. 
         [0027]    Inclusion of first idler pulley  20  in FEAD  10  at this location, allows for A/C compressor pulley  22  and crankshaft pulley  16  to be rotated in the same direction (i.e. 
         [0028]    counterclockwise) though they are proximal. If first idler pulley  20  were not included at this location, crankshaft pulley  16  may rotate in an opposing direction of A/C compressor pulley  22  (i.e. clockwise). For example, after wrapping around approximately ½ of crankshaft pulley  16 , drive belt  28  extends upward and wraps around approximately ⅓ of power steering pump pulley  14 . As there is no idler pulley between crankshaft pulley  16  and power steering pump pulley  14 , power steering pump pulley  14  may rotate in an opposing direction relative to crankshaft pulley  16 , in a clockwise direction. 
         [0029]    The structure of first idler pulley  20  is shown in greater detail in  FIGS. 2 and 3 . First idler pulley  20  has an overall flat disc-like shape with a centrally located through hole  100 , which is a generally circular space. In alternate embodiments, through hole  100  may have other shapes which correspond to the profile of the profile of the rotational axis. For example, the rotational axis may have a hexagonal profile and therefore the through hole may have a generally hexagonal shape. At an inner region surrounding through hole  100 , first idler pulley  20  includes hub  102 . An inner wall  104  of hub  102  may contact and be fixed to rotational axis  52 . A diameter D 1  of through hole  100  is substantially equal to a diameter of rotational axis  52  (not shown). 
         [0030]    A smooth belt contacting surface  110  encompasses an outer circular portion  112 . A plurality of angled spokes  108  are extended between an outer wall  106  of hub  102  and an inner wall  114  of outer circular portion  112 . Drive belt  28  is aligned with belt contacting surface  110 . Drive belt  28  has a width A and belt contacting surface  110  has a width B. Width A is less than width B. An example width A is approximately 2 mm less than width B. In alternate embodiments, the belt contacting surface may include a lip edge on one or both sides. A lip edge may substantially abut a side of the drive belt and contribute to alignment of the drive belt. In yet another embodiment, the belt contacting surface may have a central groove or multiple grooves, giving a cross section of the belt contacting surface an overall V-shape or multiple V-shapes, respectively. A central groove may also contribute to alignment of the drive belt. 
         [0031]    During operation of the vehicle wherein movement drive belt  28  is driven by generator pulley  18 , drive belt  28  may impact the belt contacting surface  110  at line of impact  120 . Contact between drive belt  28  and belt contacting surface  110  may drive rotation of first idler pulley  20 . Drive belt  28  may discontinue contact with belt contacting surface  110  at line of separation  122 . Drive belt  28  may cyclically make contact at line of impact  120  and separate at line of separation  122  with each location of belt contacting surface  110 . As such, clockwise rotation of first idler pulley  20  may be driven by movement of drive belt  28 . 
         [0032]    First idler pulley  20  is shown in greater detail in the cutaway drawing of  FIG. 3 . In  FIG. 3  a portion of outer circular portion  112  is removed to show the structure of plurality of angled spokes  108 . In this embodiment, plurality of angled spokes  108  are a series of peaks and valleys having a height with a distance of B. The width of plurality of angled spokes  108  has a distance C. A space, such as space  254  is the area between a side of first idler pulley  20  and a top of a peak (such as rounded portion  240 ) or bottom of a valley (such as rounded portion  242 ). In the example pulley of  FIG. 3 , the addition of distance C and distance E is equal to distance B. In the example of  FIG. 3 , the height of any given peak or valley in the plurality of angled spokes  108  is of equal distance as the width of belt contacting surface  110 . In alternate embodiments, the addition of C and E may not be equal to distance B. In one example, the values of A, B, C, D, and E are in the ranges 10 mm-43 mm, 12 mm-45 mm, 1 mm-4 mm, and 12 mm-24 mm, respectively. 
         [0033]    Plurality of angled spokes  108  are each connected via a rounded portion, such as rounded portion  240  and rounded portion  242 . Each rounded portion is located at a top of a peak, such as rounded portion  240 , or a bottom of a valley, such as rounded portion  242 . A straight portion, such as straight portions  244  and  246 , connects each of the rounded portions. Thus, plurality of angled spokes  108  are continuous and adjacent spokes alternate in direction. An angle between adjacent spokes  248  in plurality of angled spokes  108  is substantially equal, having an angle a. In one example, the angle a is approximately 5°-100°. In alternate embodiments, the plurality of angled spokes may exclude rounded portions and thus be discontinuous. Further, if the spokes are discontinuous, they may be angled in the same direction, rather than in alternating directions. In even another example, the angle between adjacent spokes may not be equal, and thus the angle between adjacent spokes may be varied at different locations of the pulley. 
         [0034]    Hub  102  includes four concentric circular portions with flat side walls. First circular portion  226  is innermost and fourth circular portion  220  is outermost of hub  102 . Second circular portion  222  is disposed between first circular portion  226  and third circular portion  224 . Third circular portion  224  is disposed between second circular portion  222 . In this embodiment, first circular portion  226 , second circular portion  222 , and fourth circular portion  220  all have widths of the distance B, equal to the width of outermost circular portion  112 . In alternate embodiments, the hub may include more or fewer concentric circular portions and/or the widths of each may vary. Additionally, in some embodiments may include additional spokes in a circular portion. 
         [0035]    In this example, outermost circular portion  112  may be considered a fifth circular portion and plurality of angled spokes  108  may be considered a sixth circular portion. Each circular portion has a radial length which contributes to the total radial length L of first idler pulley  20 . First circular portion  226  has a radial length K. Second circular portion  222  has a radial length J. Third circular portion has a radial length I. Fourth circular portion has a radial length H. Sixth circular portion (plurality of angled spokes  108 ) has a radial length G. Fifth circular portion (outermost circular portion  112 ) has a radial length F. In order from largest to smallest the radial lengths are as follows: G, I, H, J, F, K. In this embodiment, ranges for G, I, H, J, F, and K are 10 mm-120 mm, 5 mm-7 mm, 3 mm-4 mm, 2 mm-4 mm, and 0.1 mm-0.5 mm, repectively. In alternate embodiments, the relative sizes of each portion may be varied. 
         [0036]    Third circular portion  224  has a width which is less than distance B. An outer wall  228  of second circular portion  222  is exposed above third circular portion  224  by a distance D on both sides of the pulley (only one side shown). Therefore the width of third circular portion  224  may be represented by the equation B-2D. An inner wall  250  of fourth circular portion  220  is inclined and insects a flat side wall  252  of second circular portion  224  at an angle b, which is greater than 90°. 
         [0037]    In summary, first idler pulley  20  has an overall disc-like shape. The width of first idler pulley  20  has a distance B. First idler pulley  20  includes two ring indentations. First ring indentation  230  is disposed within hub  102  and is a flat indentation. On one side of the idler pulley, first ring indentation  230  has a depth with a distance D. Second ring indentation  232  is disposed between hub  102  and outer circular portion  112 . Ring indentation  232  is an undulating indentation, formed by plurality of angled spokes  108 . A depth of ring indentation  232  has a distance E and a width of the undulating portion has a width C. The addition of distance A and distance C is equal to distance B. 
         [0038]    The above description characterizes an idler pulley for a front end accessory drive serpentine belt system of a vehicle. The idler pulley conformation may have the advantages that spokes connecting the hub to the outermost circular portion are angled. Thus, defects due to material shrinkage and fill will impact the drive belt at an angle as the drive belt is driven over the surface of the idler pulley. This may have the effect of reduced noise generated by impact of defects against the belt. Additionally, the idler pulley may have increased material strength as the spokes are a continuous ring, rather than separate structures. 
         [0039]    It will be appreciated that the configurations disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above technology can be applied to various types of vehicles, such as small cars or trucks. In another example, the technology can be applied to hybrid vehicle or a combustion engine only vehicle. In yet another example, the pulley design may be included in other pulleys, such as the A/C compressor pulley, the second idler pulley, and/or the crankshaft pulley. Further, still the pulley design may be used in other industrial belt driven systems. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
         [0040]    The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.