Patent Publication Number: US-8973547-B2

Title: Engine starter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 U.S. National Stage of International Application No. PCT/CA2010/000760, filed May 17, 2010, and claims the benefit of U.S. Provisional Application No. 61/178,572, filed May 15, 2009, and U.S. Provisional Application No. 61/229,107, filed Jul. 28, 2009, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     INTRODUCTION 
     The present disclosure relates to an engine starter. 
     Internal combustion engines are typically started via an electric starter motor. In most conventional starting systems, the electric starter motor is equipped with a pinion gear that can be engaged to a ring gear that is mounted to a crankshaft-driven flywheel or flexplate. The pinion gear is typically maintained axially apart from the ring gear (i.e., so that the pinion gear and ring gear are disengaged from one another), but is translated into engagement with the ring gear upon activation of the electric starter motor. The electric starter motor can drive or rotate the pinion gear to cause corresponding rotation of the crankshaft (via the ring gear and the flywheel or flexplate). When the internal combustion engine starts and the electric starter motor is de-activated, the pinion gear translates out of engagement with the ring gear so that the electric starter motor is not driven by the crankshaft. 
     The limited lifespan of such starting systems is well known and can be problematic in vehicle powertrain systems that require more frequent starting (e.g., start-stop hybrids). Accordingly, an improved engine starter is desired. 
     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 teachings provide an engine starter apparatus that includes a clutch assembly and a ring gear or a pulley. The clutch assembly has a plate structure, a drive hub, a clutch element and an actuator. The actuator comprises a member that is axially movable to selectively initiate engagement of the clutch element to a circumferentially extending surface of the drive hub. The clutch element comprises a helically wound spring wire having a first end and a second end. The first end of the helically wound spring wire is configured to receive rotary power from the plate structure, while the second end is coupled to the member for rotation therewith. The ring gear or pulley is coupled to the plate structure for rotation therewith. 
     In another form, the teachings of the present disclosure provide a method for starting an engine in which a clutch assembly is provided between a starter motor and a flywheel or flex plate. The clutch assembly is engaged in response to the generation of a drag force when the starter motor is operating. 
     In a further form, the present disclosure provides an engine assembly having an engine block, a crankshaft, a lubricating oil, a flywheel or flexplate and an engine starter. The crankshaft is mounted for rotation in the engine block. The lubricating oil is disposed in the engine block and is configured to lubricate engine components including the crankshaft. The flywheel or flexplate is coupled for rotation with the crankshaft. The engine starter has a motor, a transmission and a clutch. The transmission is driven by the motor and includes an output member. The clutch is disposed axially between the crankshaft and the flywheel or flexplate. The clutch includes a clutch element that is configurable in a first state in which the output member of the transmission is not drivingly coupled to the flywheel or flexplate. The clutch element is also configurable in a second state in which the output member of the transmission is drivingly coupled to the flywheel or flexplate. The lubricating oil is not employed to lubricate the clutch 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. Similar or identical elements are given consistent identifying numerals throughout the various figures. 
         FIG. 1  is a schematic illustration of a vehicle having an engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is an exploded perspective view of a portion of the vehicle of  FIG. 1  illustrating the engine starter in more detail; 
         FIG. 2A  is an enlarged portion of the exploded perspective view of  FIG. 2  illustrating the clutch element in more detail; 
         FIG. 3  is a longitudinal section view of a portion of the vehicle of  FIG. 1  taken along the rotational axis of the crankshaft and illustrating the engine starter in more detail; 
         FIG. 4  is a cross-sectional view of a portion of an engine showing a second engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 5  is a perspective view of a portion of the vehicle of  FIG. 1  illustrating a portion of the engine starter in more detail; 
         FIG. 6  is an exploded perspective view of a portion of another vehicle illustrating a third engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 7  is an exploded perspective view of a portion of another vehicle illustrating a fourth engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 7A  is an enlarged portion of the exploded perspective view of  FIG. 7  illustrating the clutch element in more detail; 
         FIG. 8  is a longitudinal section view of a portion of the vehicle of  FIG. 7  taken along the rotational axis of the crankshaft and illustrating the fourth engine starter in more detail; 
         FIG. 9  is a perspective view of a portion of the fourth engine starter illustrating the coupling of the clutch element and the armature of the electronic actuator; 
         FIG. 10  is an exploded perspective view of a portion of another vehicle illustrating a fifth engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 10A  is an enlarged portion of the exploded perspective view of  FIG. 10  illustrating the clutch element in more detail; 
         FIG. 11  is a longitudinal section view of a portion of the vehicle of  FIG. 10  taken along the rotational axis of the crankshaft and illustrating the fifth engine starter in more detail; 
         FIG. 12  is an exploded perspective view of a portion of another vehicle illustrating a sixth engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 13  is a longitudinal section view of a portion of the vehicle of  FIG. 12  taken along the rotational axis of the crankshaft and illustrating the sixth engine starter in more detail; and 
         FIG. 14  is a perspective view of a portion of the sixth engine starter constructed in accordance with the teachings of the present disclosure illustrating the clutch element as engaged to the plate structure; 
         FIG. 15  is an exploded perspective view of a seventh engine starter constructed in accordance with the teachings of the present disclosure; 
         FIG. 16  is a longitudinal section view of the engine starter of  FIG. 15 ; 
         FIG. 17  is a perspective view of a portion of the engine starter of  FIG. 15  illustrating the connection between an armature and an end of a clutch element; 
         FIG. 18  is a perspective view in partial section of a portion of the engine starter of  FIG. 15  illustrating the plate structure in more detail; 
         FIG. 19  is an enlarged portion of  FIG. 15  illustrating the carrier and the clutch element in more detail; and 
         FIG. 20  is a plan view of a portion of the engine starter of  FIG. 15  illustrating the coupling of the clutch element, the carrier and the plate structure. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     With reference to  FIGS. 1 through 3  of the drawings, a vehicle constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The vehicle  10  can include an internal combustion engine  12  that can include an engine housing  14 , a crankshaft  16 , a flywheel  18  and an engine starter  20 . The engine housing  18  can include an engine block  26  and an engine cover  28 . The crankshaft  16  can be mounted to the engine block  26  for rotation therein. The engine cover  28  can be coupled to an end of the engine block  26  and can include an aperture  32  through which an end  34  of the crankshaft  16  can extend. An oil seal  36  ( FIG. 3 ) can be received in the aperture  32  and can form a seal between the engine cover  28  and the end of the crankshaft  16 . The flywheel  18  can be coupled for rotation with the end  34  of the crankshaft  16 . Those of skill in the art will appreciate that while the vehicle  10  is described and illustrated herein as including a flywheel, the vehicle could include a flexplate in the alternative. 
     With reference to  FIGS. 2 and 3 , the engine starter  20  can include a motor  40 , a first pulley  42 , a second pulley  44 , an endless power transmitting element  46  and a clutch  48 . The motor  40  can be powered in any desired manner (e.g., electrically, pneumatically, hydraulically) and can comprise a rotary output member  50  that can drive the first pulley  42 . The second pulley  44  can be disposed about the end  34  of the crankshaft  16  as will be discussed in detail, below. The endless power transmitting element  46  can be a belt or a chain and can engage the first and second pulleys  42  and  44  to transmit rotary power from the first pulley  42  to the second pulley  44 . In the particular example provided, the endless power transmitting element  46  is a cogged or toothed belt and the first and second pulleys  42  and  44  have corresponding teeth for engaging the teeth of the belt. It will be appreciated that other types of belts could be employed in the alternative, including a helically opposed tooth belt, a V-belt or a poly-V belt. Depending on the particular belt selected, those of skill in the art will appreciate that it may be desirable or necessary to include an appropriately shaped flange or lip on a corresponding side of one or both of the first and second pulleys  42  and  44  to maintain the belt in engagement with the first and second pulleys  42  and  44 . Moreover, those of skill in the art will further appreciate that a tensioner assembly  52  can be employed to maintain a desired amount of tension on the endless power transmitting element  46  as is shown in  FIG. 4 . The example of  FIG. 4  employs a spring-biased linear tensioner assembly  52  that is mounted to the flywheel or bell housing  54 , but those of skill in the art will appreciate that other types of tensioner assemblies could be employed in the alternative. 
     Returning to  FIGS. 2 and 3 , the clutch  48  can include a bearing  60 , a drive hub  62 , a plate structure  64 , a clutch element  66 , a friction ring  68 , a snap ring  70 , a drive plate  72  and a retaining spring  74 . The bearing  60  can be any type of bearing or bushing and can be received over an annular projection  80  on the engine cover  28  that is concentric with the aperture  32 . 
     The drive hub  62  can include a central hub  90 , a circumferentially extending outer wall member  92  and a flange member  94  that can couple the central hub  90  to the wall member  92  so as to form an annular cavity  96  between the central hub  90  and the wall member  92 . Threaded fasteners  98  can be employed to fixedly but removably couple the flywheel  18  and the central hub  90  to the end  34  of the crankshaft  16  for rotation therewith. The wall member  92  can have an interior circumferential surface  100  that can be hardened in an appropriate manner (e.g., case hardened and/or nitrided). 
     While the drive hub  62  has been illustrated and described as being formed from a suitable metal, it will be appreciated that the drive hub  62  could be formed of several discrete components that can be assembled together. For example, a relatively soft material, such as a high quality rubber, a nylon, a combination of rubber and nylon, or a thermosetting material, such as phenolic, can be coupled to a metal structure such that the relatively soft material forms the interior circumferential surface  100  for increased compliance. 
     The plate structure  64  can be coupled to the second pulley  44  in any desired manner. For example, the plate structure  64  and the second pulley  44  could be integrally formed. In the particular example provided, however, the plate structure  64  is a weldment and the second pulley  44  is fixedly coupled to an outer circumferential portion of the plate structure  64 . In this regard, the plate structure  64  can comprise a first plate member  102  and a second plate member  104 . The first plate member  102  can include an annular portion  106 , a first flange member  108  coupled to a first end of the annular portion  106 , and a second flange member  110  coupled to an opposite end of the annular portion  106 . The annular portion  106  can be sized to be received over the bearing  60  such that the bearing  60  can support the annular portion  106  (and thereby the plate structure  64 ) for rotation on the annular projection  80 . The annular portion  106  can be received in the annular cavity  96  in the drive hub  62  and can include an outer circumferential surface  114  that can be spaced apart from the interior circumferential surface  94 . The first flange member  108  can be oriented generally perpendicular to the annular portion and can extend radially inwardly therefrom. A notch  116  can be formed in the first flange member  108  and a portion of the material proximate the notch  116  can be deformed to form a helical ramp  118 . The second flange member  110  can extend radially outwardly from the annular portion  106  and can be shaped as desired so as to not contact the drive hub  62 . In the particular example provided, the second flange member  110  includes an offset zone  124  that wraps around the wall member  92  of the drive hub  62  to aid in the formation of a labyrinth that is resistant to the ingress of material into/egress of material (e.g., a lubricant) out of the annular cavity  96 . The second flange member  110  can be coupled in any desired manner (e.g., fasteners, adhesives, brazing, welding) to the second flange member  110  and can include an outer rim portion  126  to which the second pulley  44  is fixedly coupled. 
     The clutch element  66  can comprise a wrap spring that can be formed of a plurality of wraps. The clutch element  66  can be received in the annular cavity  96  between the interior circumferential surface  100  of the outer wall member  92  and the outer circumferential surface  114  of the annular portion  106  and can be frictionally engaged to the outer circumferential surface  114  of the annular portion  106 . The wrap spring can be formed of a suitable material, such as a relatively hard spring steel, and can have an appropriate cross-sectional shape, such as a generally square or generally rectangular cross-sectional shape, in which the surfaces of the cross-sectional shape are generally flat or somewhat convex in shape. It will be appreciated, however, that the wire of the wrap spring could have any desired cross-sectional shape, including a round cross-sectional shape. Moreover, the wire could be a “plain” wire, or could be coated with a desired coating (e.g., nickel plating) and/or can be lubricated with a desired lubricant, such as a grease. With additional reference to  FIG. 2A , the clutch element  66  can include a first end  130  and a second end  132  that is disposed on a side of the clutch element  66  opposite the first end  130 . With brief reference to  FIG. 5 , the first end  130  can include a first end face  134  (of the wire that forms the wrap spring); the first end  130  can extend over the ramp  118  on the first flange member  108 . Returning to  FIGS. 2 and 3 , the second end  132  can include a second end face  136  and can extend through a slot  138  formed in the plate structure  64 . In the particular example provided, the slot  138  is formed in the first plate member  102 . 
     The friction ring  68  can be a generally C-shaped member that can be received between the plate structure  64  and the engine cover  28  and engaged to the annular projection  80  on the engine cover  28 . The friction ring  68  can include projections (e.g., ribs, hooks, bumps, tabs) or apertures (e.g., holes, slots, recessed areas) that can be configured to engage the second end face  136  of the second end  132  of the clutch element  66 . In the particular example provided, the friction ring  68  includes a series of circumferentially spaced-apart projections  140  that are configured to abut the second end face  136  of the second end  132  of the clutch element  66 . 
     The snap ring  70  can be received about the friction ring  68  and can be employed to apply a compressive force to the friction ring  68  that causes the friction ring  68  to frictionally engage the annular projection  80  on the engine cover  28 . 
     With reference to  FIGS. 2 and 5 , the drive plate  72  can include a radially projecting edge  150  and a helical cover portion  152 . In the particular example provided, the helical cover portion  152  is slit or pierced and bent upwardly from a remainder of the drive plate  72  to form and expose the radially projecting edge  150 . The drive plate  72  can be fixedly coupled to the first flange member  108 , e.g., via a plurality of threaded fasteners or rivets (not shown). The first end  130  of the clutch element  66  can be received between the helical ramp  118  and the helical cover portion  152  such that the first end face  134  is abutted against the radially projecting edge  150 . 
     The retaining spring  74  can be an annular spring washer (e.g., Bellville spring washer) that can be press-fit onto the annular portion  80  of the engine cover  28  and configured to limit axial movement of the plate structure  64  and the drive plate  72  in a direction away from the engine  12  ( FIG. 1 ). 
     With reference to  FIGS. 2 ,  3  and  5 , when the crankshaft  16  is rotating to provide rotary power to the flywheel  18  and the motor  40  is not operated to drive the second pulley  44  (via the endless power transmitting element  46  and the first pulley  42 ), the clutch element  66  is retracted away from the interior circumferential surface  100  of the wall member  92  and consequently, rotary power is not transmitted from the drive hub  62  through the clutch element  66  to the plate structure  64 . 
     When the motor  40  is operated to drive the second pulley  44  (via the endless power transmitting element  46  and the first pulley  42 ) at a speed that is greater than a rotational speed of the crankshaft  16 , rotation of the drive plate  72  (which rotates with the plate structure  64 ) drives the radially projecting edge  150  into contact with the first end face  134  of the first end  130  of the clutch element  66 . Power input to the clutch element  66  travels longitudinally through the coils of the material that makes up the clutch element  66  (i.e., the coils of wire in the example provided) and rotary power is output from the clutch element  66  via the second end  132  of the clutch element  66 . In the example provided, rotary power is transmitted from the second end face  136  into a corresponding one of the spaced-apart projections  140  on the friction ring  68 . As the friction ring  68  frictionally engages the annular projection  80  on the engine cover  28 , the clutch element  66  will tend to unwind such that the coils  66   a  of the clutch element  66  engage the interior circumferential surface  100  of the wall member  92  to transmit rotary power into the drive hub  62  to thereby drive the crankshaft  16  and start the engine  12  ( FIG. 1 ). 
     It may be that the friction torque required to be generated by the friction ring  68  is higher than the torque rate of the clutch element  66 , which may in some situations prevent the clutch element  66  from returning to it&#39;s closed position. After starting the engine  12  ( FIG. 1 ), the motor  40  could be employed to reverse the rotation of second pulley  46  through a predetermined angle (relative to the crankshaft  16 ), such as an angle that is less than or equal to 45 degrees, to relieve tension on the clutch element  66  to permit it to unwind and return to a state where it is disengaged from the interior circumferential surface  100  of the wall member  92 . 
     The motor  40  can be sized to output relatively more torque than a traditional starter motor, can have a high speed capacity and/or can be controlled in a manner similar to a servo motor. The first pulley  42  can have an effective diameter that is relatively larger than the effective diameter (i.e., pitch diameter) of a pinion associated with a traditional starter so as to reduce the stress on the endless power transmitting element  46  and to reduce the rotational speed of the motor  40  when the motor  40  is driven by the engine  12  ( FIG. 1 ). The second pulley  46  can also have an effective diameter that is relatively smaller than the effective diameter (i.e., pitch diameter) of a ring gear associated with a traditional starter to more easily package the engine starter  20  into a vehicle. Moreover, the second pulley  46  can be formed of a relatively lightweight material, such as plastic or aluminum. 
     The example of  FIG. 6  is generally similar to the example of  FIGS. 1-3 , except that a ring gear  44   a  has replaced the second pulley  44  ( FIG. 2 ), a pinion gear  42   a  has replaced the first pulley  42  ( FIG. 2 ), and teeth of the pinion gear  42   a  directly engage teeth of the ring gear  44   a  to transmit rotary power between the pinion gear  42   a  and the ring gear  44   a . In some situations, the ring gear  44   a  and/or the pinion gear  42   a  can be formed of plastic or can be a plastic coated metal composite. Construction in this manner may help avoid fretting where the teeth of the pinion gear  42   a  and the ring gear  44   a  stay in stationary contact with one another and/or reduce gear mesh noise. 
     The example of  FIGS. 7 through 9  is generally similar to the example of  FIGS. 1 through 3 , except that the clutch  48   c  includes an electromagnetic actuator  200  instead of a friction ring  68  ( FIG. 2 ) and a snap ring  70  ( FIG. 2 ). The electromagnetic actuator  200  can include a coil assembly  202  that can be fixedly mounted to the engine cover  28   c , and an armature  204 . The armature  204  can be fixedly coupled to the second end  132   c  of the clutch element  66   c  and can be mounted for rotation on the annular projection  80   c  on the engine cover  28   c . In the particular example provided, the second end  132   c  of the clutch element  66   c  is oriented generally perpendicular to the coils of wire (generally parallel to the longitudinal axis of the clutch element  66   c ) and received into a slot  210  formed in the armature  204 . 
     When the crankshaft  16  is rotating to provide rotary power to the flywheel  18  and the coil assembly  202  is not activated, the clutch element  66   c  is retracted away from the interior circumferential surface  100  of the wall member  92  and consequently, rotary power is not transmitted from the drive hub  62  through the clutch element  66   c  to the plate structure  64 . 
     When the motor  40  ( FIG. 2  or  FIG. 6 ) is operated to drive the second pulley  44  (via the endless power transmitting element  46  and the first pulley  42  or via a pinion gear  42   a  and a ring gear  44   a ) at a speed that is greater than a rotational speed of the crankshaft  16 , rotation of the drive plate  72  (which rotates with the plate structure  64 ) drives the radially projecting edge  150  into contact with the first end face  134  ( FIG. 5 ) of the first end  130  of the clutch element  66   c . Power input to the clutch element  66   c  travels longitudinally through the coils of the material that makes up the clutch element  66   c  (i.e., the coils of wire in the example provided) and rotary power is output from the clutch element  66   c  via the second end  132   c  of the clutch element  66   c . As the second end  132   c  of the clutch element  66   c  is coupled to the armature  204 , the armature  204  will be driven about the annular projection  80   c  on the engine cover  28   c . Activation of the coil assembly  202  generates a magnetic field that resists rotation of the armature  204 , thereby applying a drag force that tends to cause the clutch element  66   c  to unwind such that the coils  66   a - c  of the clutch element  66   c  engage the interior circumferential surface  100  of the wall member  92  to transmit rotary power into the drive hub  62  to thereby drive the crankshaft  16  and start the engine. Upon deactivation of the coil assembly  202 , the armature  204  can rotate about the projection  80   c  such that the clutch element  66   c  unwinds and the clutch element  66   c  disengages the interior circumferential surface  100  of the wall member  92  to halt torque transmission through the clutch  48   c.    
     It will be appreciated that with appropriate motor and gear sizing, the starter system  20   c  of the example of  FIGS. 7 through 9  could be employed to provide propulsive power to a vehicle, such as “launch assist”, in which propulsive power is provided by the motor  40  ( FIG. 2  or  6 ) in addition to the engine and/or in a mode where propulsive power is provided only by the motor  40  ( FIG. 2  or  6 ). Moreover, the addition of a second electromagnetic coil (not shown) and an associated wrap clutch mechanism (not shown) on the outside of the drive hub  62   c  could be used to rotationally lock the plate structure  64  to the drive hub  62   c  to effectively drive the motor  40  ( FIG. 2  or  6 ) so that the motor  40  ( FIG. 2  or  6 ) could be employed as a generator to provide re-generative braking capabilities in which an electrical resistive load (i.e., the generation of electricity) is employed to slow the vehicle. 
     In the example of  FIGS. 10 through 11 , the clutch  48   d  can include a bearing  60   d , a drive hub  62   d , a plate structure  64   d  and a clutch element  66   d . The bearing  60   d  can be any type of bearing or bushing and can be received over the annular portion  80  of the engine cover  28   d.    
     The drive hub  62   d  can be received axially between the end  34   d  of the crankshaft  16   d  and the flywheel  18 . One or more fasteners (not shown) can be employed to secure the flywheel  18  and the drive hub  62   d  to the crankshaft  16   d  for rotation therewith. The drive hub  62   d  can include an outer circumferential surface  100   d  and a locating feature  300  that can be employed to locate the drive hub  62   d  to the rotational axis  302  of the crankshaft  16   d . The locating feature  300  can be a bore of a predetermined diameter that can matingly engage a corresponding feature  306 , such as an annular projection, that can be formed on the end  34   d  of the crankshaft  16   d . Those of skill in the art will appreciate that other types of locating features could be employed, including one or more dowels and/or shoulder bolts. The outer circumferential surface  100   d  of the drive hub  62   d  can include a first portion  310 , which can match the diameter of the outer surface  312  of the end  34   d  of the crankshaft  16   d , and a second portion  314  that can be somewhat smaller in diameter to provide radial clearance for the plate structure  64   d.    
     The plate structure  64   d  can include a main hub portion  320 , an outer annular flange  322  and an inner annular flange  324 . The main hub portion  320  can be a generally tubular structure that can be received onto the bearing  60   d  so as to be rotatably disposed on the annular projection  80   d  of the engine cover  28   d . The outer annular flange  322  can extend radially outwardly from the main hub portion  320  and the second pulley  46  (or a ring gear) can be coupled for rotation thereto. The annular inner flange  324  can include a radially inwardly extending annular portion  330  that can be coupled to an end of the main hub portion  320  opposite the engine cover  28   d , and an annular portion  332  that can be coupled to a distal end of the radially inwardly extending annular portion  330  and extend generally parallel to the main hub portion  320 . The annular portion  332  can define an interior annular clutch element engaging surface  336  having a diameter that can match that of the first portion  310  of the outer circumferential surface  100   d  of the drive hub  62   d.    
     The clutch element  66   d  can comprise a spring that can be formed of a wire that is wrapped into a plurality of wire coils. The wire can be formed of a suitable material, such as a relatively hard spring steel, and can have an appropriate cross-sectional shape, such as a generally square or generally rectangular cross-sectional shape, in which the surfaces of the cross-sectional shape are generally flat or somewhat convex in shape. It will be appreciated, however, that the wire of the clutch element  66   d  could have any desired cross-sectional shape, including a round cross-sectional shape. Moreover, the wire could be a “plain” wire, or could be coated with a desired coating (e.g., nickel plating) and/or can be lubricated with a desired lubricant, such as a grease. 
     The clutch element  66   d  can be formed with several distinct zones, including a first zone  340 , a second zone  342  and a third zone  344 . The first zone  340  can be sized to engage the interior annular clutch element engaging surface  336  such that the clutch element  66   d  is coupled for rotation with the plate structure  64   d . The third zone  344  can be sized to engage an interior annular surface  350  formed by the aperture  32  that extends through the annular projection  80   d  in the engine cover  28   d . The second zone  342  can be disposed axially between the first zone  340  and the third zone  344  and can comprise a plurality of wire coils that are spaced apart generally concentrically from the first portion  310  of the outer circumferential surface  100   d  and the outer surface  312  of the end  34   d  of the crankshaft  16   d . The clutch element  66   d  can include suitable transition zones between the between the first and second zones  340  and  342  and between the second and third zones  342  and  344 . For example, the transition zone  360  between the first and second zones  340  and  342  can include one or more wire coils that increase in diameter from the first zone  340  to the second zone  342 . 
     When the engine starter  20   d  is not being operated and the plate structure  64   d  is not being rotated at a speed that exceeds a rotational speed of the crankshaft  16   d , the wire coils of the clutch element  66   d  are not engaged to the end  34   d  of the crankshaft  16   d  or the drive hub  62   d . Accordingly, rotary power cannot be transmitted between the crankshaft  16   d  and the second pulley  46 . 
     When the engine starter  20   d  is operated to drive the plate structure  64   d  at a rotational speed that exceeds a rotational speed of the crankshaft  16   d , the clutch element  66   d  will rotate with the plate structure  64   d  as the first zone  340  is engaged to/coupled for rotation with the inner annular flange  324 . Drag caused by contact between the third zone  344  of the clutch element  66   d  and the engine cover  28   d  will cause the clutch element  66   d  to coil more tightly as the clutch element  66   d  rotates such that the wire coils of the second zone  342  contact the first portion  310  of the outer circumferential surface  100   d  of the drive hub  62   d  and possibly the outer surface  312  of the end  34   d  of the crankshaft  16   d . Engagement of the clutch element  66   d  to one or both of the first portion  310  of the outer circumferential surface  100   d  and the outer surface  312  permits rotary power to be transmitted from the plate structure  64   d  (which is driven by the second pulley  44 ) to the crankshaft  16   d  to start the engine and/or to aid in the propulsion of the vehicle. 
     In the example of  FIGS. 12 through 14 , the clutch  48   e  can include a bearing  60   e , a drive hub  62   e , a plate structure  64   e  and a clutch element  66   e . The bearing  60   e  can be any type of bearing or bushing and can be received over the annular portion  80  of the engine cover  28   e . In the particular example provided, the bearing  60   e  is configured to support the plate structure  64   e  for rotation on the annular projection  80  of the engine cover  28   e , as well as to provide a bearing surface that is suited to receive thrust forces transmitted from the plate structure  64   e  to the engine cover  28   e.    
     The drive hub  62   e  can include a central hub  90   e , a circumferentially extending outer wall member  92   e  and a flange member  94   e  that can couple the central hub  90   e  to the wall member  92   e  so as to form an annular cavity  96   e  between the central hub  90   e  and the wall member  92   e . One or more threaded fasteners (not shown) can be employed to fixedly but removably couple the flywheel  18  and the central hub  90   e  to the end  34   e  of the crankshaft  16   e  for rotation therewith. The wall member  92   e  can have an interior circumferential surface  100   e  that can be hardened in an appropriate manner (e.g., case hardened and/or nitrided). 
     While the drive hub  62   e  has been illustrated and described as being formed from a suitable metal, it will be appreciated that the drive hub  62   e  could be formed of several discrete components that can be assembled together. For example, a relatively soft material, such as a high quality rubber, a nylon, a combination of rubber and nylon, or a thermosetting material, such as phenolic, can be coupled to a metal structure such that the relatively soft material forms the interior circumferential surface  100   e  for increased compliance. 
     The plate structure  64   e  can be coupled to the second pulley  44  (or a ring gear) in any desired manner. For example, the plate structure  64   e  and the second pulley  44  could be integrally formed. In the particular example provided, however, the plate structure  64   e  is a weldment and the second pulley  44  is fixedly coupled to an outer circumferential portion of the plate structure  64   e . In this regard, the plate structure  64   e  can comprise a first plate member  102   e  and a second plate member  104   e . The first plate member  102   e  can include an annular portion  106   e  and a flange member  110   e  coupled to the annular portion  106   e  so as to extend radially outwardly therefrom. The annular portion  106   e  can be sized to be received over the bearing  60   e  such that the bearing  60   e  can support the annular portion  106   e  (and thereby the plate structure  64   e ) for rotation on the annular projection  80 . The annular portion  106   e  can be received in the annular cavity  96   e  in the drive hub  62   e  and can include an outer circumferential surface  114   e  that can be spaced apart from the interior circumferential surface  100   e . A plurality of clutch engagement features  400  can be formed onto or coupled to the annular portion  106   e . In the particular example provided, the clutch engagement features  400  comprise recesses that are formed in the outer circumferential surface  114   e . The flange member  110   e  can be shaped as desired so as to not contact the drive hub  62   e . In the particular example provided, the flange member  110   e  includes an offset zone  124   e  that wraps around the wall member  92   e  of the drive hub  62   e  to aid in the formation of a labyrinth that is resistant to the ingress of material into/egress of material (e.g., a lubricant) out of the annular cavity  96   e . The second plate member  104   e  can be coupled in any desired manner (e.g., fasteners, adhesives, brazing, welding) to the second flange member  110   e  and can include an outer rim portion  126   e  to which the second pulley  44  is fixedly coupled. 
     The clutch element  66   e  can comprise a band or clock-type spring that can comprise one or more spring elements  410  and one or more engagement members  412 . Each of the spring elements  410  can be coiled about the rotational axis of the crankshaft  16   e  and received in the cavity  96   e  between the outer circumferential surface  114   e  and the interior circumferential surface  100   e . The spring elements  410  can be configured such that they tend to uncoil and lay against the interior circumferential surface  100   e . The engagement members  412  can be coupled to the one or more of the spring elements  410  can be engaged to the clutch engagement features  400  to inhibit relative rotation between an inner end of the one or more spring elements  410  and the plate structure  64   e.    
     The one or more spring elements  410  of the clutch element  66   e  are wound in such a way that when the engine starter  20   e  is not being operated and the plate structure  64   e  is not being rotated at a speed that exceeds a rotational speed of the crankshaft  16   e , the one or more spring elements  410  of the clutch element  66   e  tend to coil more tightly due to drag forces and do not drivingly engage the interior circumferential surface  100   e  of the drive hub  62   e  such that rotary power is not transmitted between the plate structure  64   e , through the clutch element  66   e  to the drive hub  62   e . Accordingly, rotary power cannot be transmitted between the crankshaft  16   e  and the second pulley  46 . 
     When the engine starter  20   e  is operated to drive the plate structure  64   e  at a rotational speed that exceeds a rotational speed of the crankshaft  16   e , the clutch element  66   e  will rotate with the plate structure  64   e  as the engagement members  412  can be engaged to the clutch engagement features  400 . Drag forces created by contact between the one or more spring elements  410  of the clutch element  66   e  and the interior circumferential surface  100   e  of the drive hub  62   e  cause the clutch element  66   e  to uncoil such that the one or more spring elements  410  drivingly engage the interior circumferential surface  100   e  so that rotary power can be transmitted from the plate structure  64   e  (which is driven by the second pulley  44 ) to the crankshaft  16   e  to start the engine and/or to aid in the propulsion of the vehicle. 
     The example of  FIGS. 15 and 16  is generally similar to the example of  FIGS. 7 through 9 , except that the clutch is packaged somewhat differently into the engine starter and a friction material is incorporated into the electromagnetic actuator. 
     In  FIG. 15 , the engine starter  20   f  is illustrated to include a motor  40 , a pinion gear  42   a , a ring gear  44   a  and a clutch  48   f . The clutch  48   f  can include an electromagnetic actuator  200   f , a first retainer  500 , a thrust washer  502 , a bearing  60   f , a second retainer  504 , a plate structure  64   f , a carrier  508 , a clutch element  66   f , a spring  510 , a spacer  512 , and a drive hub assembly  514 . 
     The electromagnetic actuator  200   f  can include a coil assembly  202   f  and an armature  204   f . The coil assembly  202   f  can include a coil housing  520  and a coil unit  522 . 
     The coil housing  520  can define a mounting flange  530  and a mounting hub  532 . The mounting flange  530  can be fixedly coupled to the engine cover  28   f  via a set of threaded fasteners  536 . The mounting hub  532  can be disposed concentrically about the crankshaft  16  and can extend axially (i.e., along the rotational axis of the crankshaft  16 ) in a direction away from the engine cover  28   f . The mounting hub  532  can define a first annular hub member  540 , a second annular hub member  542 , and a radial wall  544  into which an annular coil groove  546  and an annular spring recess  548  can be formed. The second annular hub member  542  can be concentric with and smaller in diameter than the first annular hub member  540 . 
     The coil unit  522  can include a housing  522   a  and a coil  522   b . The housing  522  can define an inner circumferential flange ICF, an outer circumferential flange OCF and an annular channel AC disposed between the inner circumferential flange ICF and outer circumferential flange OCF. The coil  522   b  can be received into the annular channel AC. The coil assembly  202   f  can be received in the coil groove  546  and can be fixedly mounted to the coil housing  520  so as to be disposed on a side of the coil housing  520  opposite the engine cover  28   f . If desired, mating anti-rotation features, such as projections on the housing  522   a  and recesses in the coil housing  520 , can be employed to inhibit rotation of the coil unit  522  relative to the coil housing  520 . Leads  550  extending from the coil unit  522  can be routed in a desired manner, such as rearwardly through an aperture (not specifically shown) in the coil housing  520  and radially outwardly therefrom. 
     With additional reference to  FIG. 17 , the armature  204   f  can be an annular structure that can define an armature aperture  570 , one or more clutch member abutment tabs  572  and an engagement member  574  that can be abutted against a side of the second end  132   f  of the clutch element  66   f , which has been bent in a radially inward direction in the particular example provided. The clutch member abutment tab(s)  572  can be configured to abut the clutch element  66   f  on a side opposite the plate structure  64   f . In the example provided, the clutch member abutment tabs  572  are formed helically so as to engage a corresponding surface of the wire that forms the clutch element  66   f . The armature  204   f  can be mounted for rotation on the second annular hub member  542 . 
     Returning to  FIGS. 15 and 16 , the first retainer  500  can be mounted to the mounting flange  530  and can retain the armature  204   f  on the second annular hub member  542 . For example, the first retainer  500  can comprise a snap ring that can be fit to a groove  580  in the second annular hub member  542 , or could be secured to the mounting hub  532  via any conventional means, including welding, adhesives, and/or one or more threaded fasteners. The thrust washer  502  can be received between the armature  204   f  and the first retainer  500  and can form a bearing that permits the armature  204   f  to rotate without frictionally engaging the first retainer  500 . 
     The bearing  60   f  can be any type of bearing and in the particular example illustrated, comprises a bushing that is received over the first annular hub member  540 . The bearing  60   f  can have a rear lip  590 , which can be abutted against the mounting flange  530 , a front lip  592 , which can be offset axially from the rear lip  590 , and a cylindrical portion  594  that can be coupled at its opposite ends to the rear and front lips  590  and  592 . The rear and front lips  590  and  592  cooperate with the cylindrical portion  594  to define an annular channel into which the carrier  508  can be received. 
     The second retainer  504  can be mounted to the mounting flange  530  and can retain the bearing  60   f  on the first annular hub member  540 . For example, the second retainer  504  can comprise a snap ring that can be fit to a groove  600  in the first annular hub member  540 , or could be secured to the mounting hub  532  via any conventional means, including welding, adhesives, and/or one or more threaded fasteners. 
     With additional reference to  FIG. 18 , the plate structure  64   f  can include an annular member  900  and an inner hub  902 . The annular member  900  can be coupled to the ring gear  44   a  in any desired manner, such as a weld along its outer diameter that fixedly couples it to the ring gear  44   a . The annular member  900  can define a central aperture  610  into which the inner hub  902  can be received. In the example provided, the inner hub  902  can include an outer cylindrical hub surface  910 , a plate member groove  644  ( FIG. 16 ), a carrier groove  914  ( FIG. 16 ), and a clutch mount  612 . The plate member groove  644  can be formed into the outer cylindrical hub surface  910  and can be configured to fit snugly into the central aperture  610  of the annular member  900  to locate the inner hub  902  in a concentric manner to the annular member  900 . The inner hub  902  may be fixedly coupled to the annular member  900  in a desired manner, such as welding. The carrier groove  914  can be formed into the outer cylindrical hub surface  910  adjacent the plate member groove  644 . The clutch mount  612  can comprise a mount aperture  920 , a mount wall  922  and a reaction member  924 . The mount aperture  920  can be formed into the outer cylindrical hub surface  910  such that the reaction member  924  is defined by an edge of the mount aperture  920  and the mount aperture  920  is situated between the mount wall  922  and the annular member  900 . The reaction member  924  can be disposed at a predetermined orientation relative to the central (rotational) axis of the inner hub  902 . For example, the reaction member  924  can be perpendicular to a circle that is centered on the rotational axis of the inner hub  902  and which intersects the reaction member  924 . The inner hub  902  can be received in the annular channel of the bearing  60   f.    
     With reference to  FIGS. 15 ,  16  and  19 , the carrier  508  can be formed so as to be radially compliant (i.e., being capable of radially expanding and contracting). In the particular example provided, the carrier  508  is split radially such that a gap  630  is disposed between two circumferential ends (i.e., the first and second ring ends  632  and  634 , respectively). The carrier  508  can define an inner circumferential surface  950 , a mounting lip  952 , which can extend radially inwardly from the inner circumferential surface  950 , a rear abutment surface  640 , which can be abutted against a front face of the annular member  900 , a clutch member abutment surface  642  and a clutch member mount  646  ( FIG. 19 ). The inner circumferential surface  950  can be abutted to the outer cylindrical hub surface  910  and the mounting lip  952  can be received into the carrier groove  914  to locate the carrier  508  axially relative to the plate structure  64   f . The rear abutment surface  640  can be configured to abut the annular member  900 . All or portions of the clutch member abutment surface  642  can be configured to abut the clutch element  66   f . In the particular example provided, the clutch member abutment surface  642  is helically formed along the rotational axis of the crankshaft  16  such that a thickness of the carrier  508  proximate the first ring end  632  is larger than a thickness of the carrier  508  proximate the second ring end  634 . The clutch member mount  646  can be configured to retain the clutch element  66   f , as well as to direct the first end  130   f  of the clutch element  66   f  into engagement with the plate structure  64   f  as will be described in more detail, below. In the example provided, the clutch member mount  646  is configured to be received into the mount aperture  920  in the clutch mount  612  of the plate structure  64   f  and includes a track  650 , a radially inner wall  652  and first and second end surfaces  654  and  656 , respectively. The track  650  can be formed (e.g., recessed into) the first ring end  632  to a level that corresponds to the level of the clutch member abutment surface  642  on the second ring end  634 . It will be appreciated that all or portions of the track  650  could be formed in a helical manner that matches the helix of the clutch member abutment surface  642 , or that all or portions of the track  650  could be formed parallel to the rear abutment surface  640 . The track  650  can be contoured in a desired manner, such as in a radially inward manner, and can terminate at the reaction member  924  of the clutch mount  612  on the plate structure  64   f  such that the first end  130  of the clutch element  66   f  directly contacts the reaction member  924 . Alternatively, the track  650  could terminate prior to the reaction member  924  such that load transmitted to the first end  130   f  of the clutch element  66   f  is initially transmitted between the reaction member  924  and the first end surface  64  of the clutch mount  612 . Construction in this latter manner may be advantageous when, for example, it is necessary or desirable to increase the surface area over which power is transmitted between the clutch element  66   f  and the plate structure  64   f.    
     Returning to  FIGS. 15 and 16 , the spring  510  can be configured to bias the armature  204   f  toward the first retainer  500  and in the particular example provided, comprises a wave spring that is received in the annular spring recess  548  that is formed in the radial wall  544  of the mounting hub  532 . The spacer  512  can be disposed between the spring  510  and the armature  204   f  and can cooperate with the spring  510  to cause a desired biasing force to be applied to the armature  204   f . If desired, the spacer  512  could also function as a thrust washer. 
     The drive hub assembly  514  can include a hub member  670 , a drive hub  62   f  and a radial flange  674 . 
     The hub member  670  can be co-formed with the drive hub  62   f , but in the particular example provided, comprises a discretely formed member having a first pilot portion  680 , a bolt flange  682 , and a second pilot portion  684 . The first pilot portion  680  can be configured to center the clutch  48   f  to the crankshaft  16 . In the particular example provided, the first pilot portion  680  comprises a bore  690  that matingly engages a cylindrical projection  692  on the crankshaft  16  but it will be appreciated that various other types of centering means can be employed, including pins, or that an assembly tool (not shown) may be employed in lieu of a mating connection between the first pilot portion  680  and the crankshaft  16 . The bolt flange  682  can define a plurality of bolt holes  696  through which bolts  698  can be received to fixedly but removably couple the drive hub assembly  514  to the crankshaft  16 . If desired, a shield member  700  may be received between the crankshaft  16  and the hub member  670  to shield an oil seal  702  that is located between the engine cover  28   f  and the crankshaft  16 . The hub member  670  can extend axially away from the crankshaft  16  and through the mounting hub  532  such that the second pilot portion  684  extends therefrom. The flywheel  18   f  can be configured to matingly engage the second pilot portion  684  to center the flywheel  18   f  relative to the rotational axis of the crankshaft  16 . 
     The drive hub  62   f  can include a central hub  90   f , a circumferentially extending outer wall member  92   f  and a flange member  94   f  that can couple the central hub  90   f  to the wall member  92   f  so as to form an annular cavity between the central hub  90   f  and the wall member  92   f . The central hub  90   f  can be received over the hub member  670  and the bolts  698  that couple the hub member  670  to the crankshaft  16  can also be employed to fixedly couple the central hub  90   f  to the hub member  670  for rotation therewith. The wall member  92   f  can have an interior circumferential surface  100   f  that can be hardened in an appropriate manner (e.g., case hardened and/or nitrided). The radial flange  674  can be fixedly coupled to and extend radially outwardly from the drive hub  62   f.    
     The radial flange  674  can be fixedly coupled to an outer surface of the circumferentially extending outer wall member  92   f  and can comprise a plurality of female threaded nuts  708  that are spaced apart about the circumference of the radial flange  674 . Threaded fasteners  710  can be employed to fixedly but removably couple the flywheel  18   f  to the radial flange  674 . 
     It will be appreciated, however, that the radial flange  674  may be omitted altogether and that the bolts  698  that couple the hub member  670  to the crankshaft  16  could also be employed to couple the flywheel  18   f  to the crankshaft  16 . 
     When the engine is to be started, the motor  40  can be energized and can transmit rotary power via the pinion  42   a  and the ring gear  44   a  to the plate structure  64   f , which will cause rotation of the clutch element  66   f  about the mounting hub  532 . Simultaneously with the energization of the motor  40 , the coil  522   b  can be energized to cause the armature  204   f  to travel axially and frictionally engage the coil housing  520  of the coil assembly  202   f . As the second end  132  of the clutch element  66   f  is engaged to the armature  204   f  and as the first end  130  of the clutch element  66   f  is engaged to the rotating plate structure  64   f , rotary motion will be transmitted through the clutch element  66   f  so that the armature  204   f  would tend to rotate. Frictional engagement between the armature  204   f  and the coil housing  520  is sufficiently strong so as to resist rotation of the armature  204   f  (and therefore the second end  132  of the clutch element  660  and causes the wire of the clutch element  66   f  to uncoil or unwind such that it frictionally engages the interior circumferential surface  100   f  of the drive hub  62   f  to transmit rotary power into the drive hub  62   f  to thereby drive the crankshaft  16 . 
     When the engine has been started, the motor  40  and the coil  522   b  can be de-energized to disengage the clutch  48   f . The spring  510  can bias the armature  204   f  away from the coil housing  520  when the coil  522   b  has been de-energized such that the armature  204   f  will rotate with the wire coils of the clutch element  66   f . The plate structure  64   f , however, will slow relative to the rotational speed of the crankshaft  16  and drive hub  62   f , which will cause the first end  130  of the clutch element  66   f  to slow and consequently the wire of the clutch element  66   f  will coil or wind more tightly such that it disengages the interior circumferential surface  100   f  of the drive hub  62   f  to permit the plate structure  64   f  to be rotationally decoupled from the drive hub  62   f  and the crankshaft  16 . 
     If provided, the radial compliance of the carrier  508  can aid in the installation of the carrier  508  to the inner hub  902  of the plate structure  64   f , as well as permit a small degree of rotation between the plate structure  64   f  and the carrier  508 /clutch element  66   f  and/or radial contraction of the carrier  508  when rotary power is initially transmitted from the plate structure  64   f  to the carrier  508  to engage the clutch assembly. Such compliance can render the carrier  508  more tolerant of manufacturing tolerances while ensuring that the carrier  508  is not overloaded during engine starting. 
     It will be appreciated that in each of the above-described engine starters, a friction material could be employed on the surfaces of one or more of the components to control engagement of the clutch assembly. In  FIGS. 15 through 19 , for example, the friction material can be part of the armature  204   f  and/or of another structure that is configured to limit movement of the armature  204   f  in a predetermined direction (e.g., toward the coil  522   b ), such as one or both of the outer circumferential flange OCF and the inner circumferential flange ICF of the housing. In the particular example provided, however, a friction material F is coupled only to the surface S of the armature  204   f  that is configured to frictionally engage the inner and outer circumferential flanges ICF and OCF of the housing  522   a . The friction material F can be formed of any desired thickness, such as a thickness of 1.0 mm or less. For example, the friction material F can have a thickness that is greater than or equal to 0.15 mm and less than or equal to 0.4 mm, such as a maximum thickness that is less than or equal to 0.25 mm, and can provide a coefficient of static friction that is greater than or equal to 0.12. Exemplary materials include MF701 and HM200 friction papers marketed by Miba Hydramechanica of Sterling Heights, Mich. It will be appreciated that while the MF701 and HM200 are friction papers for wet (i.e., oil lubricated) applications, various other types of friction materials, including those configured for dry (i.e., non-lubricated) applications could be employed. While optional, the use of a desired friction material F can provide several benefits, including less slipping at the interface between the armature  204   f  and the housing  522   a , which we believe will reduce the time required for engagement of the clutch assembly as well as provide enhanced durability. 
     It will be appreciated that in each of the above-described engine starters, a lubricating oil in the engine block that is employed to lubricate engine components (including the crankshaft) is not employed to lubricate the clutch element. Configuration in this manner can be advantageous in some situations as oil seals for containing the engine lubricating oil are not required. Consequently, the starter systems described above may be employed in non-traditional areas, including the front of the engine. It will be appreciated, however, that lubrication of the clutch element may be necessary and/or desirable in some situations and as such, the scope of present disclosure is not to be limited to engine starters having a clutch element that is not lubricated with engine lubricating oil. 
     It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein so that one of ordinary skill in the art would appreciate from this disclosure that features, elements and/or functions of one example may be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the teachings of the present disclosure, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims.