Patent Abstract:
A pulley has a hub and a rim. The hub is configured to be mountable on a driving shaft. A driving connection between the hub and rim is provided. In a first embodiment, a drive mechanism is operable to configure the rim between a circular profile and a non-circular profile. The non-circular profile produces a counteracting torque to offset load torques produced by the engine. The drive mechanism can be electrical, inertial, hydraulic or any combination thereof. In a second embodiment, the rim is fixed with a non-circular profile.

Full Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a pulley for drive system of an internal combustion engine. More particularly, the invention relates to pulley having a shape that counteracts and substantially reduces mechanical vibrations, in particular but exclusively in internal combustion engines. 
       DESCRIPTION OF THE RELATED ART 
       [0002]    The serpentine accessory belt of the internal combustion engine drives devices like an alternator, an air conditioning compressor, a water pump, and a power steering pump. The energy is provided by the engine&#39;s crankshaft and is transmitted to driven components via a poly-V belt. This power delivery is not smooth. It occurs with the speed fluctuating intensely particularly at low rpm. Crankshaft torsionals are caused by the cycles of the internal combustion engine (intake, compression, combustion and exhaust). Particularly, the combustion cycle affects the amplitude of crankshaft torsionals. 
         [0003]    When the frequency of these vibrations is close to the natural frequency of the drive, system resonance occurs. At resonance, the torsional vibrations and the span tension fluctuations are at their maximum. Tension fluctuations at resonance can easily cause the belt to slip on the crankshaft pulley or on the other pulleys depending on the magnitude of tension fluctuations, wrap angle, friction factor, etc. The belt slip is undesired because it disrupts power transmission, produces noise and reduces belt life. Vibrations may also cause wear of other components and result in other undesirable effects. 
         [0004]    A novel approach to attenuating vibrations in internal combustion engines has been proposed in WO 03/046413. In this commonly assigned patent publication, it is proposed that a synchronous drive system in an engine be provided with a pulley or sprocket that has a non-circular profile. The non-circular profile produces an opposing fluctuating corrective torque. The angular position of the non-circular profile coincides with an angular position for which a maximum elongation of the drive span coincides with a peak value of the fluctuating load torque of the rotary load. 
         [0005]    In the prior publication, the non-circular pulley or drive sprocket is fixed. However in many engines, as the RPM increases, the engine usually has smaller fluctuations in load torque. Thus, the need to introduce a counteracting torque as provided by the non-circular profile also diminishes. With a fixed profile, the counteracting torques will nonetheless be introduced into the drive system. 
       SUMMARY OF THE INVENTION 
       [0006]    It is desirable to provide a rotor or pulley for a drive apparatus, wherein the rotor or pulley has a non-circular profile and an indicia marking enabling the pulley to be installed on a crankshaft in a desired orientation. 
         [0007]    It is desirable to provide a rotor or pulley for a drive apparatus, wherein the rotor or pulley is able to alter its profile between a non-circular profile and a circular profile, so that the rotor can be dynamically altered depending on engine conditions. 
         [0008]    According to one aspect of the invention, there is provided a pulley having a hub configured to be mountable on a driving shaft and a rim. There is a driving connection between the hub and rim. A drive assembly is operable to configure the rim between a circular profile and a non-circular profile. The drive assembly can be electrical, inertial, hydraulic or any combination thereof. 
         [0009]    According to another aspect of the invention, there is provided a method for operating an engine. The engine has an endless drive system including a configurable crankshaft pulley. The method includes the steps of sensing engine conditions, such as RPM, accessory drive belt tension, to determine whether torque loads in the endless drive are in excess or about to be in excess of a predetermined value and responsively altering the profile of the crankshaft pulley between a circular and a noncircular profile to generate a counteracting torque in the belt. 
         [0010]    According to another aspect of the invention, there is provided a pulley having a hub and a rim. The hub is configured to be mounted on a driving shaft, such as a crankshaft. The rim has a non-circular profile. The pulley has indicia thereon for orienting the pulley in a predetermined position relative to the driving shaft. 
         [0011]    According to another aspect of the invention, there is provided a pulley having a hub and a rim. The hub is configured to be mountable on a driving shaft. The rim has a non- circular profile. The hub has means for orienting the hub in a predetermined position relative to the driving shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0012]    Advantages of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
           [0013]      FIG. 1  is a schematic view of a front of a vehicle engine with an endless belt extending through a serpentine path around a plurality of conventional pulleys and a pulley of the present invention; 
           [0014]      FIG. 2  is a partial perspective view of an engine incorporating a pulley of the present invention; 
           [0015]      FIG. 3  is a graph illustrating the relationship between torsional vibrations of a typical four cylinder engine resulting from an air conditioner compressor and an alternator; 
           [0016]      FIG. 4  is perspective view of a first embodiment of a pulley of the present invention; 
           [0017]      FIG. 5  is a partial elevational view of the pulley of  FIG. 4 ; 
           [0018]      FIG. 6  is schematic view of an endless drive system similar to  FIG. 1  but having a different arrangement of pulley elements; 
           [0019]      FIG. 7  is a plan view of a second embodiment of the present invention, with the inertia elements in the non-circular profile position; 
           [0020]      FIG. 8  is a plan view of the embodiment of  FIG. 7 , with the inertia elements in the circular profile position; 
           [0021]      FIG. 9  is a partial sectional view of the embodiment of  FIG. 7 , with the inertial element in the circular profile position; 
           [0022]      FIG. 10  is a partial sectional view of the embodiment of  FIG. 7 , with the inertial element in the non-circular profile position; 
           [0023]      FIG. 11  is perspective view of a third embodiment of the present invention; 
           [0024]      FIG. 12  is a partial plan view of the embodiment of  FIG. 11 ; 
           [0025]      FIG. 13  is a perspective view, partially in sectional, of fourth embodiment of the present invention; 
           [0026]      FIG. 14  is sectional view of the embodiment of  FIG. 13 ; and 
           [0027]      FIG. 15  is a perspective view of a fifth embodiment of the pulley or rotor of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    Referring to  FIGS. 1 and 2 , an endless belt  10  is shown extending through a serpentine path. Typically, the endless belt  10  is mounted on the front of an engine  11  for driving various accessories or components. Alternatively, the endless belt  10  may also be a chain, particularly timing systems, as is known in the art. The curved serpentine path is defined by six pulleys  12 ,  14 ,  16 ,  18 ,  20 ,  22  and a tensioner pulley  24 . The pulleys  12 ,  14 ,  16 ,  18 ,  20  are shown here by way of example, although not every internal combustion engine includes all of these pulleys. In the present example, the pulleys are as follows: a crank shaft pulley  12 , an alternator pulley  14 , an idler pulley  16 , a power steering pulley  18 , an air conditioning pulley  20  and a water pump pulley  22 . Depending on the location and size of the pulley  12 - 24  various percentages of the periphery of each of the pulleys  12 - 24  are engaged by the belt  10 . 
         [0029]    The belt  10  can transfer in excess of 3000 Newtons of force for driving the various components of the internal combustion engine. Typical forces required to drive an accessory drive or timing drive vary widely with the engine and application. However, in most cases, a typical force range is somewhere in the region of 300 N to 500 N, when measured on the “slack side” of the belt. A typically low applied belt tension would be in the 100 N range. A typically high force range is somewhere in the range of 1000 to 2000 N. 
         [0030]    Referring to  FIG. 3 , a graph illustrates the relationship between the torsional vibrations in degrees versus the speed of the engine in RPM on two components of the engine, namely the alternator pulley and the air conditioner compressor pulley for a typical four cylinder engine. As is illustrated, relatively high torsional vibrations are observed at about 500 to 750 RPM and as the engine speed increases, the torsional vibrations diminish. 
         [0031]    Referring now to  FIGS. 4 and 5 , a rotor or pulley  12  of the present invention is illustrated. The pulley  12  generally comprises a hub  32 , a rim  34  and a plurality of circumferentially spaced torque transfer sleeves  36 . Inside each sleeve  36  is a drive actuator  38 . 
         [0032]    Hub  32  is configured for mounting on the end of the crankshaft of the engine. Hub  32  is oriented on the crankshaft relative to the top dead center mark. Hub  32  is provided with an axle  33 . A pair of copper sleeves  35 ,  37  is mounted for rotation with the axle  33  and hub  32 . An electrical connection  39  is provided from sleeve  35  to each of the actuators  38 , presenting a first voltage rail. An electrical connection  41  is provided from sleeve  37  to each of the actuators  38 , presenting a second voltage rail. A pair of brushes  43 ,  45  is mounted to engage the sleeves  35 ,  37 , respectively, to provide current to the sleeves  35 ,  37  as the hub  32  rotates. Each of the brushes  43 ,  45  are connected to a satellite controller  52 . 
         [0033]    Rim  34  is generally ring shaped, having an outer circumferential surface  42 . The outer circumferential surface has poly-V grooves, which are conventional in the art. Rim  34  is relatively stiff but is capable of a degree of flexibility or malleability. Preferably, rim  34  is molded from an organic resin material, such as Nylon. Additional reinforcement materials, such as glass fibres, nano particles, may be added to increase strength. On a conventional sized engine, the rim  34  must be capable of repeatably flexing about 4 mm in diameter along the major diameter. 
         [0034]    Each of sleeves  36  consists of an inner sleeve  44  and an outer sleeve  46 . The inner sleeves  44  are mounted to the hub  32  and the outer sleeves  46  are mounted to the rim  34 . The sleeves  44 ,  46  slide relative to each other yet provide a driving connection between the hub  32  and the rim  34  enabling torque to be transferred from the crankshaft  13  to the belt  10 . Sleeves  36  provide a flexible driving connection between the hub  32  and the rim  34 . As is now apparent to those skilled in the art, the particular arrangement of the sleeves could be reversed without departing from the present invention. Additionally, other flexible driving arrangements, such as a rubber ring may also be utilized to provide the flexible driving connection. 
         [0035]    The number of sleeves  36  will depend upon the number of cylinders of the engine. For example, a four cylinder or V-8 engine will preferably have four or multiples of four actuators  36 . An inline six or V-6 engine will preferably have three or multiples of three actuators  36 . 
         [0036]    Inside each sleeve is a drive actuator  38 . In the present embodiment, actuator  38  is a shape memory alloy (SMA) actuator, as is well know in the art. Examples of such actuators are detailed in U.S. Pat. No. 6,390,878, www.steadlands.com and http://www.cim.mcgill.ca/˜grant/sma.html. Other drive actuators such as solenoids may also be substituted. 
         [0037]    Upon application of an electrical current, the actuator  38  will responsively expand or retract depending upon the polarity of the current. The actuators  38  will be electrically connected such that certain ones of the actuator  38  will contract and others will expand upon application of an electric current. As illustrated in  FIG. 5 , two diametrically opposed actuators will expand and the other two diametrically opposed actuators will contract, causing the rim  34  to move from a circular configuration to a non-circular profile or configuration, in this example, oval. 
         [0038]    The oval profile of rim  34  has at least one reference radii, in the present example reference radii  50   a  and  50   b,  which together form the major axis  50  of the oval and a minor axis  51 . Each reference radius  50   a,    50   b  passes from the centre of the rotor  12  and through the centre of the respective protruding portion  52 ,  53 . The angular position of the non- circular profile is related to a reference direction of the rotor  12 , the reference direction being the direction of a vector or imaginary line  54  that bisects the angle or sector of wrap of the continuous loop belt  10  around the rotor  12 . This vector that bisects the angle of wrap is in the same direction as the hub load force produced by engagement of the belt  10  with the rotor  12  when the belt drive system is static. It should be appreciated, however, that the hub load force direction changes dynamically during operation of the belt drive system. The timing of the non-circular profile is set to be such that, at the time when the torsionals are at a maximum, the peak torsional point, the angular position of the reference radius  50   a  is about 90° (four or eight cylinders) to 120° (three or six cylinders) from the reference direction of the angle of wrap bisection  54  ( FIG. 6 ), taken in the direction of rotation of the rotor  12 . 
         [0039]    The magnitude of the eccentricity of the non-circular profile is determined with reference to the amplitude of the peak torsional. In some arrangements the amplitude of the torsional may be substantially constant, and in other arrangements the amplitude of the fluctuating torsional may vary, as illustrated in  FIG. 3 . Where the amplitude of the fluctuating torsional is constant, the magnitude of the eccentricity is determined with reference to that substantially constant amplitude of fluctuating torsional. Where the amplitude of the fluctuating torsional varies, the value thereof which is used to determine the magnitude of the eccentricity will be selected according to the operating conditions in which it is desired to eliminate or reduce the unwanted vibrations. 
         [0040]    For each engine, the dynamic peak torsional point can be measured relative to the crankshaft angle. The orientation of the rotor  12  of the present invention relative to the crankshaft can be predetermined. In particular, the minor reference radius  50  is positioned within the first quadrant of the belt wrap a with the peak torsional point. 
         [0041]    Referring to  FIG. 6 , a schematic of a typical engine is illustrated. The arrangement is similar to the schematic of  FIG. 1 . Both arrangements are provided for illustration purposes only. Tensioner  56  is provided with a position sensor  58 . Position sensor  58  measures the relative position of the tensioner pulley  24  and generates a tensioner position signal. Take-up pulley  60  is also provided with a position sensor  62 . Position sensor  62  measures the relative position of the take-up pulley and generates a take-up pulley signal. The tensioner position signal and the take-up pulley signal are proportional to belt tension on the respective sides of pulley  12  or the present invention. The two signals are fed into a controller  64 . Controller  64  also receives inputs  66  from other vehicle sensors to provide information such as engine speed, and engine load. Controller  64  compares the signals to determine if the engine is experiencing relatively high torsionals. The controller  64  responsively sends a signal to satellite processor  52  to energize the actuators  38  in a first polarity, altering the profile or configuration of the pulley  12  from circular to non-circular. Once the controller  64  determines that the engine is operating in a range outside of the relatively high torsionals, the controller  64  sends a signal to the satellite processor  52 , which responsive energizes the actuators  38  in a second polarity, opposite the first polarity, returning the pulley  12  to a circular profile or configuration. 
         [0042]    Referring to  FIGS. 7-10 , a second embodiment of the present invention is illustrated. The pulley  212  is conventional in design in that the pulley  212  has a hub  232  and a rim  234 . Preferably, pulley  212  is made of sheet steel according to U.S. Pat. No. 4,273,547. The outer rim  234  is provided with cut-outs or openings  236 , preferably diametrically opposed. A series of inertia elements  238  are pivotally mounted on the hub  232  at pins  240 . Each inertia element  238  has head portion  244  and a tail portion  246 . The inertia elements  238  are each connected to a spring  242  at the tail end  246 . The head portion has a series of V-grooves, matching the V-grooves of the outer rim  234 . The inertia elements  238  are mounted to pivot between a non-circular profile position ( FIGS. 7 and 10 ) and a circular profile position ( FIGS. 8 and 9 ). 
         [0043]    The spring rate of springs  238  and the mass of the inertia elements  238 , particularly the ratio of the tail portion  246  versus the head portion  244 , is selected such that at low RPM the spring  242  urges the inertia element  238  to pivot about pin  240  to extend the head portion  244  outwardly. In this non-circular profile position, the head portion  244  extends outwardly from the circumferential extent of the outer rim  234 , presenting a series of lobes or bumps. At higher RPM, the inertial forces overcome the spring forces causing the inertia elements  238  to pivot about pin  240  to retract head portion  244 , presenting a generally circular profile on the outer rim  234 . 
         [0044]    Optionally, the springs  238  could be replaced or supplemented with actuators, preferably SMA actuators. 
         [0045]    As with the first embodiment, the number of inertia elements depends on the number of cylinders of the engine. For four and eight cylinder engines, the pulley  212  of the present invention has two or four inertia elements  238 . For six or twelve cylinder engines, the pulley  212  has three or six inertia elements  238 . Positioning of the lobes or bumps relative to TDC is determined in the same fashion as the first embodiment. The present embodiment is passive device, only responsive to RPM of the engine. 
         [0046]    Referring to  FIGS. 11 and 12 , a third embodiment of the present invention is illustrated. This embodiment  312  is similar to the first embodiment in that it is a dynamic or active device. In this embodiment, a piezoelectric stack  338  is mounted to the hub  332 . The rim  334  has a series of apertures in the V-grooves. The stack  338  has a head portion  344  that is configured to correspond with the poly-V grooves of rim portion  334 . The pulley  312  is provided with an electrical connection similar to the first embodiment. Upon energizing the stack  338 , the head portion  344  extends outwardly to present a non-circular profile. Upon de- energizing the stack  338 , the head portion  344  retracts inwardly to present a circular profile. 
         [0047]    Referring to  FIGS. 13 and 14 , a fourth embodiment of the pulley of the present invention is illustrated. Pulley  412  has a hub  432  connected to a rim  434 . Preferably, hub  434  has a non-circular profile having a major axis  450  of an oval. Preferably, hub.  432  and rim  434  are relative stiff but flexible, molded with an organic resin material. Hub  432  must be capable of stretching along the minor axis about 4 mm. Apertures could be provided in hub  432  to allow for such movement. 
         [0048]    The center of the spreader  452  operatively engages a rod  454  the is connected to an hydraulic plunger  456  of cylinder  457 . Cylinder  457  communicates with the oil lubricating network of the engine via passageway  458 . Return spring  460  provides a return force on the hydraulic plunger  456 . 
         [0049]    A spreader  452  is mounted along the minor axis of the oval. The spreader  452  is generally sigma-shaped in cross section with the upper and lower portions engaging the inner face of rim  434 . 
         [0050]    At low RPM, the engine oil pressure is also low. The hydraulic forces acting on plunger  456  is low allowing the spring  460  to retract rod  454 . In this condition, the outer rim  434  will present a non-circular profile. As the RPM increases, so does the engine oil pressure. The hydraulic cylinder  456  begins to overcome the bias of the spring  460  to extend the rod  454 . As the rod  454  extends, the spreader  452  urges the minor axis of the outer rim  434  to move outwardly to present a generally circular profile. 
         [0051]    Referring to  FIG. 15 , a fifth embodiment is illustrated. In this embodiment, the rotor  512  has a non-circular profile having a major axis  550  defined by reference radii  550   a  and  550   b  and a minor axis  551 . The rotor  512  has a hub  532  and an outer rim  534 . The rotor  512  is provided with an orientation indicia or other marking to enable the rotor  512  to be installed on an end of crankshaft in a predetermined orientation. Hub  532  has a reference mark  552 , which is located at a predetermined angle θ relative to one of the major reference radii  550   a  or  550   b.  Alternatively, the hub  532  can be provided with a key way  554  enabling the pulley  512  to be mounted on the crankshaft in only one predetermined orientation. Other known methods of mounting devices in a predetermined orientation may be apparent to those skilled in the art and are incorporated herein. 
         [0052]    Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended clairns, the invention may be practiced other than as specifically described.

Technology Classification (CPC): 5