Patent Publication Number: US-RE47454-E

Title: Clutched driven device and associated clutch mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 U.S. National Stage of International Application No. PCT/CA2011/000981, filed on Aug. 24, 2011, and claims the benefit of U.S. Provisional Application No. 61/376,489, filed on Aug. 24, 2010. The entire disclosures of the above applications are incorporated herein by reference. 
    
    
     INTRODUCTION 
     The present disclosure relates to a clutched driven device and an associated clutch mechanism. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     It is often desired to power a device with rotary power that is transmitted from a prime mover either directly or through an endless power transmitting element, which could employ a belt, a chain and/or a toothed gear. Such devices could, for example be connected to the engine of a motor vehicle via an accessory drive or a timing drive and could include a pump (e.g., water pump, vacuum pump, power steering pump, air compressor, air conditioning compressor), a means for generating electricity (e.g., alternator, generator, starter-alternator, starter-generator), and/or a fan, for example. 
     It will be appreciated that in situations when the output of the device is not needed or desired, operation of the device will be associated with reduced efficiency of the prime mover. In an automotive context for example, it may not be necessary to operate the engine water pump when the engine is cold and is being started and as such, the operation of the engine water pump when the engine is cold and being started reduces the overall fuel efficiency of the engine. To overcome this drawback, it was known in the art to provide a clutch to selectively operate the device. Such clutches typically required some sort of power, usually electrical power, to permit rotary power to be transmitted through the clutch to drive the device. More recently, several types of clutches have been developed by Litens Automotive Partnership that can be configured to transmit rotary power to a driven device in a normal or unpowered state and inhibit transmission of rotary power to the driven device in a power state that uses a relatively low-power input. 
     While such clutches are suitable for their intended purposes, such clutches are nonetheless susceptible to improvement. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     In a first aspect of the present disclosure, a clutched driven device is provided having a wrap spring that is disposed radially inwardly of a bearing that supports a first rotary clutch portion relative to a second rotary clutch portion. In one exemplary form, the present teachings provide a clutched driven device having a clutch assembly with a first rotary clutch portion, a second rotary clutch portion, a bearing, a wrap spring and an actuator. The first rotary clutch portion has a drive member with an interior clutch surface. The first and second rotary clutch portions are rotatably disposed about a rotary axis of the clutched driven device. The bearing is received between the first and second rotary clutch portions. The wrap spring is disposed radially inwardly of the bearing and has a first end, a second end opposite to the first end, and a plurality of helical coils that extend between the first and second ends. The first end is configured to transmit rotary power to the second rotary clutch portion. The helical coils are received against the interior clutch surface. The actuator is configured to selectively initiate coiling of the wrap spring to cause the helical coils of the wrap spring to disengage the interior clutch surface to a predetermined extent. The actuator includes an actuator input member. The actuator input member is rotatable about the rotary axis and has a spring mount, which engages the second end of the wrap spring, and a brake rotor. The actuator is selectively operable to generate a brake force that is applied to the brake rotor to resist rotation of the actuator input member about the rotary axis. 
     In a second aspect of the present disclosure, a clutched driven device is provided having a brake band that is moved via a pivot arm to provide a drag force that controls operation of a clutch assembly. In an exemplary form, the present teachings provide a clutched driven device having a clutch assembly with a first rotary clutch portion, a second rotary clutch portion, a wrap spring and an actuator. The first rotary clutch portion has a drive member with an interior clutch surface. The first and second rotary clutch portions are rotatably disposed about a rotary axis of the clutched device. The wrap spring has a first end, a second end opposite to the first end, and a plurality of helical coils that extend between the first and second ends. The first end is configured to transmit rotary power to the second rotary clutch portion. The helical coils are received against the interior clutch surface. The actuator is configured to selectively initiate coiling of the wrap spring to cause the helical coils of the wrap spring to disengage the interior clutch surface to a predetermined extent. The actuator includes an actuator input member that is rotatable about the rotary axis and has a spring mount, which engages the second end of the wrap spring, and a brake rotor. The actuator further includes a brake shoe and a pivot arm. The brake shoe is a band that extends at least partly about a circumference of the brake rotor. The pivot arm is coupled to at least one end of the band and is configured to selectively engage the band to the brake rotor. 
     In a third aspect of the present disclosure, a clutched driven device is provided having a clutch assembly with a wrap spring and an actuator having a cable for controlling engagement of the wrap spring. In an exemplary form, the present teachings provide a clutched driven device having a clutch assembly with a first rotary clutch portion, a second rotary clutch portion, a wrap spring and an actuator. The first rotary clutch portion has a drive member with an interior clutch surface. The first and second rotary clutch portions are rotatably disposed about a rotary axis of the clutched device. The wrap spring has a first end, a second end opposite to the first end, and a plurality of helical coils that extend between the first and second ends. The first end is configured to transmit rotary power to the second rotary clutch portion. The helical coils are received against the interior clutch surface. The actuator is configured to selectively initiate coiling of the wrap spring to cause the helical coils of the wrap spring to disengage the interior clutch surface to a predetermined extent. The actuator includes an actuator input member that is rotatable about the rotary axis and has a spring mount, which engages the second end of the wrap spring, and a brake rotor. The actuator further includes a cable that is movable to control rotation of the brake rotor relative to the first clutch portion. 
     In a fourth aspect of the present disclosure, a clutched driven device is provided having a clutch assembly with a wrap spring and an actuator. The actuator comprises a brake rotor and a linear motor for selectively applying a drag torque to the brake rotor that controls engagement and/or disengagement of the wrap spring. In an exemplary form, the present teachings provide a clutched driven device with a clutch assembly that includes a first rotary clutch portion, a second rotary clutch portion, a wrap spring and an actuator. The first rotary clutch portion has a drive member with an interior clutch surface, the first and second rotary clutch portions are rotatably disposed about a rotary axis of the clutched device, the wrap spring has a first end, a second end opposite to the first end, and a plurality of helical coils that extend between the first and second ends, the first end is configured to transmit rotary power to the second rotary clutch portion, the helical coils are received against the interior clutch surface, the actuator is configured to selectively initiate coiling of the wrap spring to cause the helical coils of the wrap spring to disengage the interior clutch surface to a predetermined extent, the actuator comprising an actuator input member and a linear motor, the actuator input member is rotatable about the rotary axis and has a spring mount, which engages the second end of the wrap spring, and a brake rotor, the linear motor has an output member, and wherein the linear motor is operated to move the output member to generate a brake force that is applied to the brake rotor to resist rotation of the actuator input member about the rotary axis. 
     The clutched driven device in accordance with the teachings of the fourth aspect of the present disclosure:
         may further comprise a bearing that is received between the first and second rotary clutch portions and supports the first rotary portion for rotation on the second rotary clutch portion and the wrap spring may optionally be disposed radially inwardly of the bearing;   may further comprise a working device that includes at least one of a pump, a fan and a means for generating electricity, the working device having an input shaft coupled to the second clutch portion for rotation therewith;   may be configured such that the actuator includes a brake shoe that engages the brake rotor to generate the brake force, and optionally: the actuator may further comprise a solenoid that is operable for moving the brake shoe into and/or out of contact with the brake rotor; the brake shoe may be mounted to an output member of the solenoid; the brake shoe may be coupled to the output member through at least one of a cable and a linkage; the actuator may further comprise a fluid-powered cylinder that is operable for moving the brake shoe into and/or out of contact with the brake rotor; the brake shoe may comprise a band that is wrapped at least partly around the brake rotor; the actuator may comprise a rotary motor that is operable for moving the brake shoe into and/or out of contact with the brake rotor; the rotary motor may be coupled to the brake shoe through at least one of a cable, a lead screw, and a rack-and-pinion; the actuator may further comprise a phase change material that has a first volume when the phase change material is in a first phase and a second volume when the phase change material is in a second phase that is different from the first phase, and wherein the first and second phases are selected from a group consisting of a solid phase, a liquid phase and a gaseous phase; the phase change material may be wax; and/or the actuator may further comprise a heater; and/or   may be configured such that the actuator comprises a coil and an armature, wherein the coil is operated to move the armature to generate the brake force, and wherein the armature is the output member and optionally the armature may be non-rotatably but axially movably coupled to the brake rotor and/or the coil may be disposed in a coil housing that is contacted by the armature to generate the brake force.       

     In a fifth aspect of the present disclosure, a clutched driven device is provided having a clutch assembly with a wrap spring and an actuator for controlling engagement and/or disengagement of the wrap spring to selectively transmit rotary power through the clutch assembly. The actuator comprises a brake rotor and a helical coil spring whose diameter can be changed to engage or disengage the brake rotor to selectively apply a drag torque to the brake rotor that controls engagement and/or disengagement of the wrap spring. In an exemplary form, the present teachings provide a clutched driven device with a clutch assembly having a first rotary clutch portion, a second rotary clutch portion, a wrap spring and an actuator. The first rotary clutch portion has a drive member with an interior clutch surface. The first and second rotary clutch portions are rotatably disposed about a rotary axis of the clutched device. The wrap spring has a first end, a second end opposite to the first end, and a plurality of helical coils that extend between the first and second ends. The first end is configured to transmit rotary power to the second rotary clutch portion. The helical coils are received against the interior clutch surface. The actuator is configured to selectively initiate coiling of the wrap spring to cause the helical coils of the wrap spring to disengage the interior clutch surface to a predetermined extent. The actuator includes an actuator input member, which is rotatable about the rotary axis, and a brake rotor. The actuator input member has a spring mount that engages the second end of the wrap spring. The actuator further includes a brake shoe that is movable in a radial direction to engage the brake rotor. The brake shoe includes a coil spring element that can be coiled and/or uncoiled to selectively apply a drag torque to the brake rotor. 
     The clutched driven device in accordance with the teachings of the fifth aspect of the present disclosure may further comprise a drum actuator that is rotatable to control coiling and uncoiling of the coil spring 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 longitudinal section view of a driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a front exploded perspective view of a portion of the driven accessory of  FIG. 1 ; 
         FIG. 3  is a rear exploded perspective view of a portion of the driven accessory of  FIG. 1 ; 
         FIG. 4  is a perspective view of a portion of the driven accessory of  FIG. 1  illustrating a second rotary clutch portion in more detail; 
         FIG. 5  is a longitudinal section view of a portion of the driven accessory of  FIG. 1 ; 
         FIG. 6  is a rear perspective view of a portion of the driven accessory of  FIG. 1  illustrating a wrap spring and a carrier in more detail; 
         FIG. 7  is a longitudinal section view of a second driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 8  is a longitudinal section view of a third driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 9  is a rear perspective view of a fourth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 10  is a rear perspective view of a portion of the driven accessory of  FIG. 9 ; 
         FIG. 11  is a front perspective view of a portion of the driven accessory of  FIG. 9 ; 
         FIG. 12  is rear perspective view of a portion of the driven accessory of  FIG. 9 ; 
         FIG. 13  is a rear perspective view of a fifth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 14  is a lateral section view illustrating the driven accessory of  FIG. 13  in more detail; 
         FIG. 15  is a rear perspective view of a sixth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 16  is a right side perspective view of a portion of the driven accessory of  FIG. 15 ; 
         FIG. 17  is a rear perspective view of a portion of the driven accessory of  FIG. 15 ; 
         FIG. 18  is a rear perspective view of a portion of the driven accessory of  FIG. 15 ; 
         FIG. 19  is a top perspective view of a portion of the driven accessory of  FIG. 15 ; 
         FIG. 20  is a bottom perspective view of a portion of the driven accessory of  FIG. 15 ; 
         FIG. 21  is a rear perspective view of a portion of the driven accessory of  FIG. 15 ; 
         FIG. 22  is a section view illustrating a portion of a seventh driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 23  is a front perspective view illustrating a portion of an eighth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 24  is a section view illustrating a portion of a ninth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 25  is a longitudinal cross section illustrating a portion of a tenth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 26  is a side elevation view of an eleventh driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIG. 27  is a side elevation view of a twelfth driven accessory constructed in accordance with the teachings of the present disclosure; 
         FIGS. 28 and 29  are side elevation views of a thirteenth driven accessory constructed in accordance with the teachings of the present disclosure in which  FIG. 28  depicts the linear motor in a retracted condition and  FIG. 29  depicts the linear motor in an extended condition; 
         FIG. 30  is a rear elevation view a portion of a fourteenth driven accessory constructed in accordance with the teachings of the present disclosure; and 
         FIG. 31  is longitudinal section view of a portion of a fifteenth driven accessory constructed in accordance with the teachings of the present disclosure. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     With reference to  FIGS. 1 and 2  of the drawings, a clutched driven device or accessory constructed in accordance with the teachings of the present disclosure is generally indicated by reference numeral  10 . The clutched driven device  10  can comprise an input member  12 , a substantially conventional accessory portion  14  and a clutch assembly  16 . In the particular example provided, the accessory portion  14  is a water pump assembly  20 , but those of skill in the art will appreciate that the depiction of a water pump assembly  20  is merely illustrative of one application of the present teachings and that the present teachings have application to various other types of engine accessories, such as fans, means for generating electricity (e.g., alternators, generators, starter-alternators, starter-generators), other types of pumps (e.g., air conditioning compressors, power steering pumps, vacuum pumps, air compressors), blowers, super chargers, power-take offs and accessories that are driven by other power sources, including motors (e.g., electrically-power or fluid-powered motors). Moreover, while the present teachings are depicted in an automotive or vehicle context, it will be appreciated that the teachings of the present disclosure have application to drive systems (i.e., systems for transferring motion, including systems that transfer rotary motion) generally. 
     The input member  12  can be configured to receive rotary power from an endless power transmitting member. Examples of various endless power transmitting members includes belts, chains, and gears. In the particular example provided, the input member  12  comprises a pulley sheave  22  that is configured to receive rotary power from a belt (not shown). 
     The water pump assembly  20  can include a housing  30 , an input shaft  32 , a bearing set  34 , a seal system  36  and an impeller  38 . The housing  30  can be configured to mount the clutched driven device  10  to a prime mover, such as an engine. The input shaft  32  can include an input end  40  and an output end  42  that is located opposite the input end  40 . The bearing set  34  can be disposed between the housing  30  and the input shaft  32  and can support the input shaft  32  for rotation relative to the housing  30 . The seal system  36  can comprise one or more sets of seals that are configured to inhibit ingress of contamination (e.g., dirt, debris, moisture) into the bearing set  34  and/or egress of lubrication from the bearing set  34 . The impeller  38  can be fixedly coupled to the output end  42  of the input shaft  32  for rotation therewith. 
     With reference to  FIGS. 1 through 3 , the clutch assembly  16  can comprise a first rotary clutch portion  50 , a second rotary clutch portion  52 , a bearing  54 , a wrap spring  56 , a carrier  58  and an actuator  60 . 
     The first rotary clutch portion  50  can be configured to be coupled to the input member  12  for rotation therewith about a rotary axis  70 . The first rotary clutch portion  50  can have a drive member  74  with an interior clutch surface  76 . In the particular example provided, the first rotary clutch portion  50  comprises a tubular hub  78  and a radial flange  80  that is fixedly coupled to and extends radially outwardly from a rear end of tubular hub  78 . The interior clutch surface  76  can be formed on an inside circumferential surface of the tubular hub  78  so that it is concentrically disposed about the rotary axis  70 . The radial flange  80  can be fixedly coupled to the input member  12  in any desired manner, such as welds or threaded fasteners  82 . As another example, the radial flange  80  can be integrally and unitarily formed with the input member  12  (i.e., as a one-piece component). 
     The second rotary clutch portion  52  can be configured to transmit rotary power to the input shaft  32  of the water pump assembly  20 . In the particular example provided, the second rotary clutch portion  52  comprises an outer annular wall  90 , an inner annular wall  92 , at least one drive lug  94  ( FIG. 4 ) and an end wall  96  that connects the outer and inner annular walls  90  and  92  to one another. The outer annular wall  90  can be disposed concentrically about the tubular hub  78  of the first rotary clutch portion  50 , while the inner annular wall  92  can be disposed concentrically within the tubular hub  78 . The inner annular wall  92  can be non-rotatably coupled to the input end  40  of the input shaft  32  in any desired manner, such as an interference fit, a weld, spline teeth and/or a threaded fastener. The drive lug(s)  94  can be coupled to one or more of the outer annular wall  90 , the inner annular wall  92  and the end wall  96  for rotation therewith. In the particular example provided, the drive lugs  94  are co-formed with the inner annular wall  92  and the end wall  96  but it will be appreciated, however, that the drive lugs  94  could be formed on another structure, such as a thrust washer, that is assembled to (and non-rotatably coupled to) one or more of the outer annular wall  90 , the inner annular wall  92  and the end wall  96 . 
     The bearing  54  can be received between the first and second rotary clutch portions  50  and  52  and can support the first rotary clutch portion  50  for rotation about the second rotary clutch portion  52 . In the example provided, the bearing  54  is engaged to a radially inside surface of the outer annular wall  90  and a radially outside surface of the tubular hub  78 . The bearing  54  can be any type of bearing, but in the example provided is a sealed bearing having two rows of bearing elements  100 a,  100 b that are spaced axially apart from one another along the rotary axis  70 . 
     With reference to  FIGS. 3, 5 and 6 , the wrap spring  56  can be formed of an appropriate wire, which can have a generally square or rectangular cross-sectional shape. The wire that forms the wrap spring  56  can be uncoated (i.e., plain) or could be coated with a suitable material that can, for example, help to control friction, wear, and/or heat. The wrap spring  56  can be disposed radially inwardly of the bearing  54  and can have a first end  110 , a second end  112  that is opposite to the first end  110 , and a plurality of helical coils  114  that can extend between the first and second ends  110  and  112 . The helical coils  114  can be received against the interior clutch surface  76 . In the particular example provided, the helical coils  114  are press-fit to the interior clutch surface  76  but it will be appreciated that other types of fits may be employed in the alternative. Moreover, it will be appreciated that all of the helical coils  114  need not be fitted to the interior clutch surface  76  in the same manner. For example, some of the helical coils  114  may employ an interference, while there may clearance or varying levels of interference between the remaining helical coils an the interior clutch surface  76 . The first end  110  can be configured to transmit rotary power from the helical coils  114  to the second rotary clutch portion  52  as will be discussed in more detail, below. The second end  112  can include a control tang  118  that can be coupled to the actuator  60  as will be discussed in more detail below. 
     The carrier  58  can be formed of a suitable material, such as steel or plastic, and can comprise a flange portion  120 , a sleeve portion  122 , a groove  124  and a carrier abutment wall  126 . The flange portion  120  can be an annular structure having a front surface  130 , which can abut the end wall  96  of the second rotary clutch portion  52 , and a rear surface  132  that can abut the adjacent one of the helical coils  114  of the wrap spring  56 . In the example provided, portion of the rear surface  132  that abuts the wrap spring  56  is helically shaped to match the contour of the helical coils  114  of the wrap spring  56 . The sleeve portion  122  can be an annular structure that can extend axially from the flange portion  120 . The sleeve portion  122  can be sized to be received in the helical coils  114  of the wrap spring  56  to support one or more of the helical coils  114  and/or to maintain the carrier  58  and the first end  110  of the wrap spring  56  about the rotary axis  70 . The groove  124  can be configured to receive the first end  110  of the wrap spring  56  and can extend through the circumference of the sleeve portion  122  and optionally through the carrier abutment wall  126 . The carrier abutment wall  126  can abut an abutting face  140  ( FIG. 4 ) on one of the drive lugs  94  on the second rotary clutch portion  52  and if the groove  124  extends through the carrier abutment wall  126  (as is shown in the example provided), an axial end face  142  of the wire that forms the wrap spring  56  can also abut the abutting face  140  ( FIG. 4 ) on the one of the drive lugs  94  ( FIG. 4 ). 
     With reference to  FIGS. 1, 3 and 5 , the wrap spring  56  can be wound such that the helical coils  114  tend to uncoil or expand radially outwardly when rotary power is transmitted through the clutch assembly  16 . More specifically, rotation of the input member  12  can cause corresponding rotation of the drive member  74 , which in turn can tend to rotate the wrap spring  56  due to engagement of the helical coils  114  with the interior clutch surface  76 . Rotary power input to the wrap spring  56  can be transmitted to the second rotary clutch portion  52  (via the first end  110  of the wrap spring  56  and/or the carrier  58 ), which will tend to rotate the input shaft  32  of the accessory portion  14 . Because the input shaft  32  of the accessory portion  14  does not spin without resistance (rotation of the input shaft  32  permits the accessory portion  14  to produce work), the helical coils  114  of the wrap spring  56  tend to uncoil or expand radially outwardly to better grip the interior clutch surface  76 . Accordingly, this example of the clutch assembly  16  is self-activating. 
     With reference to  FIGS. 1, 3 and 5 , the actuator  60  can be configured to selectively initiate coiling of the wrap spring  56  to cause the helical coils  114  to at least partly disengage the interior clutch surface  76 . More specifically, actuation of the actuator  60  can pull on the second end  112  of the wrap spring  56  to cause one or more of the helical coils  114  to coil more tightly or contract radially inwardly. In the example provided, the actuator  60  comprises an actuator input member  140 , a drive motor  142  and a brake shoe  144 . 
     The actuator input member  140  can comprise a hub member  150  and a brake rotor  152 . The hub member  150  can be a tubular structure that can be received between the inner annular wall  92  of the second rotary clutch portion  52  and the tubular hub  78 . The hub member  150  can have a spring mount  156  that can engage the second end  112  of the wrap spring  56 . In the present example, the spring mount  156  comprises a longitudinally extending slot  158  that is formed in the hub member  150 . The tang  118  ( FIG. 6 ) on the second end  112  of the wrap spring  56 , which can extend radially inwardly from an adjacent one of the helical coils  114 , can be received into the slot  158  so that rotation of the actuator input member  140  in a predetermined direction relative to the second end  112  of the wrap spring  56  causes coiling of the helical coils  114 . The brake rotor  152  can be an annular structure that can be coupled to the hub member  150  extend radially outwardly therefrom. The brake rotor  152  can have a rotor surface  160 . 
     The actuator input member  140  can be configured to rotate about the rotary axis  70  substantially with the first rotary clutch portion  50  such that the actuator input member  140  rotates with or lags slightly behind the first rotary clutch portion  50  as will be discussed in more detail below. Any desired means may be employed to couple the actuator input member  140  to the first rotary clutch portion  50  in a way that permits limited rotation of the actuator input member  140  relative to the first rotary clutch portion  50 . For example, receipt of the tang  118  ( FIG. 6 ) on the second end  112  of the wrap spring  56  into the slot  158  can provide sufficient rotational coupling of the actuator input member  140  to the first rotary clutch portion  50  to cause the actuator input member  140  to substantially rotate with the first rotary clutch portion  50 . In the particular example provided, however, a frictional interface is provided between the first rotary clutch portion  50  and the actuator input member  140  that creates a drag force that tends to drive the actuator input member  140  as the first rotary clutch portion  50  rotates, as well as helps to “energize” the helical coils  114  so that they uncoil/expand radially to further engage the interior clutch surface  76 . In the particular example provided, an O-ring seal  170 , which is received in a seal groove  172  formed in the hub member  150 , frictionally engages both the first rotary clutch portion  50  and the hub member  150 . If desired, one or more seals may be employed to seal the cavity between the first and second rotary clutch portions  50  and  52  into which the wrap spring  56  is disposed. In the particular example provided, a second O-ring seal  176  seals an interface between the inner annular wall  92  of the second rotary clutch portion  52  and the hub member  150 , while the O-ring seal  170  seals an interface between the hub member  150  and the tubular hub  78 . It will be appreciated that any desired type of seal may be employed for one or both of the O-ring seals  170  and  176 , such as a quad ring seal, an X ring seal, a lip seal, a dynamic seal, an overmold, etc. If desired, a suitable lubricant, such as a coating, a dry-film lubricant, a grease, oil and/or a traction fluid, can be employed to lubricate the helical coils  114  and the interior clutch surface  76 . 
     To control axial endplay of the actuator input member  140  relative to the second rotary clutch portion  52  and/or to retain the carrier  58  and provide axial clamping force on the carrier  58  and the first end  110  of the wrap spring  56 , various endplay control techniques can be employed. For example, a thrust ring  180  can be disposed between the second rotary clutch portion  52  and a front axial surface of the actuator input member  140  and a retaining ring  182 , which can be received in a ring groove  184  in the second rotary clutch portion  52 , can limit movement of the actuator input member  140  in an axial direction away from the end wall  96 . 
     The drive motor  142  can be mounted to the housing  30  ( FIG. 1 ) of the accessory portion  14  ( FIG. 1 ) and can be configured to selectively drive the brake shoe  144  into frictional engagement with the rotor surface  160  of the brake rotor  152 . In the example provided, the drive motor  142  is a linear motor, such as an electrically powered solenoid, but it will be appreciated that other types of drive motors (or linear motors) could be employed in the alternative, including cylinders. Also in the example provided the drive motor  142  has an output member  196  that is configured to translate along an actuator axis  198  that is oriented perpendicular to the rotary axis  70 . 
     It will be appreciated that the drive motor  142  can be operated to drive the brake shoe  144  into contact with the rotor surface  160  of the brake rotor  152  to generate drag (i.e., a friction force) that causes the actuator input member  140  to rotate relative to the first rotary clutch portion  50  such that the tang  118  ( FIG. 6 ) of the second end  112  of the wrap spring  56  is pulled in a rotational direction that causes one or more of the helical coils  114  to coil or contract radially inwardly such that the wrap spring  56  disengages the interior clutch surface  76  to a predetermined extent. In the present example, contact between the brake shoe  144  and the rotor surface  160  is configured to cause relative rotation of the brake rotor  152  relative to the first rotary clutch portion  50  through a limited angular offset while the brake rotor  152  continues to rotate with the first rotary clutch portion  50  (albeit in a slightly lagging behind condition defined by the angular offset). It will be appreciated, however, that if desired, contact between the brake shoe  144  and the rotor surface  160  could halt rotation of the brake rotor  152  such that the brake rotor  152  is maintained in a stationary or non-rotating condition while the first rotary clutch portion  50  rotates. 
     The brake shoe  144  can be mounted to the output member  196  of the drive motor  142  for translation therewith. In the example provided, the brake shoe  144  is depicted as a pad, but it will be appreciated that the brake shoe  144  could comprise other structures, such as a friction roller that is rotatably mounted to the output member  196 , or could be co-formed with the output member  196 . 
     While the clutch assembly  16  has been illustrated and described as employing a linear motor that is oriented generally perpendicular to a rotational axis of a brake rotor and a brake shoe that contacts a portion of a circumferentially extending surface of the brake rotor, it will be appreciated that a driven accessory constructed in accordance with the teachings of the present disclosure may be constructed somewhat differently. 
     For example, the drive motor  142 a can be oriented such that the actuator axis  198 a is parallel to the rotary axis  70  as is shown in  FIG. 7 . In this example, the rotor surface  160 a is formed on a radially extending surface of the brake rotor  152 a rather than on a circumferentially extending surface as in the example of  FIGS. 1 through 6 . 
     The example of  FIG. 8  is generally similar to that of  FIG. 7 , except that the drive motor  142 b comprises an annular cylinder  200  that is disposed concentrically about the input shaft  32  and has a piston  202  that is powered by a pressurized fluid, such as air, water or oil to translate the piston  202  along an actuator axis that is coincident with the rotational axis of the input shaft  32 . A source of pressurized fluid could be communicated to the interior of the annular cylinder  200  to cause movement of the piston  202 , or in the alternative, that fluid could be withdrawn from the cylinder  200  to create a pressure differential that causes ambient air pressure to move the piston  202 . It will be appreciated that the piston  202  can be non-rotatably housed in the annular cylinder  200 , and that the brake shoe  144 b could be mounted to or integrally formed with the annular end face of the piston  202 . 
     Various cylinder or cylinder-like devices could be substituted for the particular cylinder that is illustrated in  FIG. 8  and described above. For example, the cylinder  200  need not have an annular configuration and that in such case, the cylinder could be mounted such that the longitudinal axis of the cylinder is offset from but parallel to the rotational axis of the clutched driven device  10 b. As another example, the cylinder could have a “pneumatic muscle” configuration in which changes in the pressure of the working fluid in the cylinder can contract or elongate the cylinder in a predefined manner. 
     Another example is illustrated in  FIGS. 9 through 12  where the brake shoe  144 c comprises a band  220  that is wrapped at least partly about the circumference of the brake rotor  152 c. In this example, a first end  224  of the band  220  is coupled to the output member  196 c of the drive motor  142 c, while a second, opposite end  226  of the band  220  is fixedly coupled to a bracket  230  that is employed to mount the drive motor  142 c to the housing  30  ( FIG. 1 ). It will be appreciated that operation of the drive motor  142 c moves the output member  196 c such that the band  220  is tightened about the rotor surface  160 b of the brake rotor  152 c. 
     Still another example is illustrated in  FIGS. 13 and 14  where the brake shoe  144 d comprises a band  220 d, the drive motor  142 d is mounted such that the actuator axis  198 d is transverse to the rotational axis  70  of the driven accessory, and a pivot arm  250  couples the output member  196 d of the drive motor  142 d to the band  220 d. In the example provided, the drive motor  142 d is fixedly mounted to a bracket  258 , and the pivot arm  250  is pivotally mounted to the bracket  258  via a pivot pin  260 . The output member  196 d of the drive motor  142 d can be pivotally coupled to a first end  262  of the pivot arm  250 . The band  220 d can have first and second attachment portions  264  and  266 , respectively, and a band body  268  that can be wrapped about the rotor surface  160 d of the brake rotor  152 d. It will be appreciated that the band  220 d can be coupled to the pivot arm  250  in any desired manner that permits the band  220 d to tighten and frictionally engage the rotor surface  160 d when the drive motor  142 d is in one operational state (e.g., powered or operated) and frictionally disengaged from the rotor surface  160 d when the drive motor  142 d is in a second operational state (e.g., unpowered or not operated). For example, one of the first and second attachment portions  264  and  266  could be coupled to the pivot arm  250  for movement therewith while the other one of the first and second attachment portions  264  and  266  could be coupled to the bracket  258  such that pivoting of the pivot arm  250  about the pivot pin  260  causes the band  220 d to frictionally engage and disengage the rotor surface  160 d. Alternatively, both the first and second attachment portions  264  and  266  can be coupled to the pivot arm  250 . In the example provided, the first attachment portion  264  is coupled via a pin  280  to the pivot arm  250  at a first location between the pivot pin  260  and the first end  262 , while the second attachment portion  266  is coupled to the pivot arm  250  via a pin  282  at a second location between the pivot pin  260  and a second end  284  that is opposite the first end  262 . The second location is spaced further from a pivot axis  290  (defined by the pivot pin  260 ) than the first location to multiply the amount by which so that the first location will move relative to the pivot pin  260  by an amount that is greater than the amount by which the second location will move relative to the pivot pin  260  so that the band  220 d can be engaged to the rotor surface  160 d. 
     A further example is illustrated in  FIGS. 15-21  in which the brake shoe  144 e is a brake spring  300  that can be selectively engaged to a drum actuator  302  by the drive motor  142 e. The drive motor  142 e can be mounted to a bracket  306  that can be fixedly coupled to a non-rotating structure, such as the housing  30  ( FIG. 1 ). The bracket  306  can have a tubular hub  310  that can define a first tang slot  312 . The brake spring  300  include a first tang  320 , a second tang  322  and a plurality of helical coils  324  between the first and second tangs  320  and  322 . The first tang  320  can extend from the helical coils  324  in a radially inward direction, while the second tang  322  can extend from the helical coils  324  in an axial direction. The brake spring  300  can be received over the tubular hub  310  and the first tang  320  can be received in the first tang slot  312 . The drum actuator  302  can be an annular structure into which the brake spring  300  can be received (i.e., such that the helical coils  324  of the brake spring  300  are received between the drum actuator  302  and the tubular hub  310 . The drum actuator  302  can define a second tang slot  330  into which the second tang  322  can be received. Accordingly, it will be appreciated that rotation of the drum actuator  302  relative to the bracket  306  will cause the helical coils  324  of the drum spring  300  to expand radially outwardly (i.e., uncoil) or contract radially inwardly (i.e., coil more tightly). Any desired means may be employed to transmit motion from the drive motor  142 e to the drum actuator  302  but in the particular example provided, the output member  198 e of the drive motor  142 e is coupled to the drum actuator  302  via a linkage  334 . The brake rotor  152 e can be received between the helical coils  324  such that the rotor surface  160 e extends circumferentially about the helical coils  324 . It will be appreciated that operation of the drive motor  142 e to rotate the drum actuator  302  in a first direction relative to the bracket  306  can expand or uncoil the helical coils  324  such that they frictionally engage the rotor surface  160 e, while rotation of the drum rotor  302  in a second, opposite direction relative to the bracket  306  can contract or coil the helical coils  324  such that they do not frictionally engage the rotor surface  160 e. 
     While the driven accessories have been described above as employing a clutch assembly with a linear motor that comprises a solenoid and an armature or output member, it will be appreciated that the linear motor could be configured somewhat differently. For example,  FIGS. 22 and 23  illustrate portions of driven accessories that are generally similar to those of  FIGS. 14 and 11  except for the configuration of the linear motor. 
     In  FIG. 22 , the drive motor  142 f comprises Bowden cable  400  having an outer sleeve  402 , which is mounted in a stationary manner relative to the housing  30  ( FIG. 1 ), and a cable  404  that is slidingly received within the outer sleeve  402 . A first end  410  of the cable  404  can be coupled to the first end  262  of the pivot arm  250 , while a second, opposite end  412  of the cable  404  can be coupled to a rotary motor  414  that is configured to drive the cable  404  relative to the outer sleeve  402 . In this example, the motor  414  comprises a device with an axially movable output member  416  that is coupled to the second end  112  of the cable  404 . If desired, a spring can be employed to bias the cable  404  into a desired position. 
     In  FIG. 23 , the drive motor  142 g also comprises a Bowden cable  400 , but the second end  412  of the cable  404  is mounted or wrapped about a control rotor  450  whose rotational position relative to a stationary object (e.g., the housing  30  ( FIG. 1 ) is controlled by a motor  456  having a rotary output. The motor  456  could be a stepper motor that could be configured to directly rotate the control rotor  450 , but in the particular example provided, the motor  456  comprises a relatively small, high speed, low torque motor that drives a transmission  458  through a flexible cable  460 . The transmission  458  can have any desired reduction drive for transmitting rotary power to the control rotor  450 . In the example provided, the transmission  458  comprises a worm drive that outputs rotary power to the control rotor  450 . 
     The example of  FIG. 24  is generally similar to that of  FIG. 22  except that the linear motor  520  is schematically illustrated and can be formed of a material that changes its shape and/or length when exposed to an electronic or magnetic signal. The material could be a shape metal material, a bimetallic material (e.g., bimetallic strip), an electrostrictive material or a magnetostrictive material. A controller  522  could be employed to produce an electronic signal and/or to control a magnetic field generator  524  to produce a magnetic field and/or to control a heater  526  to produce heat that is suited for controlling the shape and/or length of the material. 
     In the example of  FIG. 25 , the drive motor  142 j and the brake shoe  144 j of the actuator  60 j are received into the brake rotor  152 j. The brake shoe  144 j can be formed of a suitable plastic and can have an annular shape with a split formed radially through one side (such that the brake shoe  144 j is C-shaped). The drive motor  142 j, which comprises a heater  530 , which could be a wire heating element, and an element  532  formed of a shape memory material or a bi-metallic material, can be encapsulated into the brake shoe  144 j and non-rotatably mounted to the water pump assembly  20  ( FIG. 1 ). 
     Operation of the heater  530  can cause the element  532  to deflect radially outwardly to drive the brake shoe  144 j into engagement with the rotor surface  160 j of the brake rotor  152 j. It will be appreciated that the drag force produced by contact between the brake shoe  144 j and the rotor surface  160 j can cause the clutch assembly  16 j to halt the transmission of rotary power between the input member  12  and the input shaft  32  ( FIG. 1 ) in a manner that is similar to that which is described in detail above. The element  532  itself and/or a resilient characteristic of the material that forms the brake shoe  144 j can act as a return spring to cause the brake shoe  144 j to disengage the rotor surface  160 j when the element  532  has cooled. 
     While the drive motor  142 j and the brake shoe  144 j of the actuator  60 j have been illustrated and described as being configured to cooperate with the brake rotor  152 j to create a drag force on a circumferentially extending interior surface of the brake rotor  152 j, it will be appreciated that the drive motor  142 j and the brake shoe  144 j could be configured to cooperate with the brake rotor  152 j to create a drag force on a circumferentially extending exterior surface of the brake rotor  152 j (i.e., the brake shoe  144 j could be disposed radially outwardly of the rotor surface  160 j and could contract radially inwardly to engage the rotor surface  160 j and expand radially outwardly to disengage the rotor surface  160 j). 
     In  FIG. 26  the linear motor comprises a motor  550  having a rotary output member that rotates a lead screw  552  to move a brake shoe  144 k into contact with a rotor surface  160 k of the brake rotor  152 k. 
     In  FIG. 27  the linear motor comprises a motor  560  having an output member that rotates a toothed pinion  562  that is in meshing engagement with a toothed rack  564 . The brake shoe  144 m is mounted to an end of the toothed rack  564  and can be selectively driven into contact with the rotor surface  160 m on the brake rotor  152 m. It will be appreciated that in the alternative, the brake shoe  144 m need not be mounted directly to the toothed rack  564  but rather could be mounted another element that is driven or moved via the toothed rack  564 . 
     In  FIGS. 28 and 29 , the linear motor comprises a commercially available phase change actuator having an actuator housing  600 , an output member  602 , a phase change material  604 , a heater  606 , and a compliant member  608 . The phase change material  604 , the heater  606  and the compliant member  608  can be received into the actuator housing  600 . The output member  602  can be slidably received in the actuator housing  600  and can be engaged to the compliant member  608 . The phase change material  604  can be a material that is configured to change its volume in response to a change in its state (e.g., solid, liquid). In the particular example provided, the phase change material  604  is a wax that can be disposed about the compliant member  608 . The heater  606  can be coupled to the actuator housing  600  and can be configured to change the phase of the phase change material  604  (e.g., melt). In the particular example provided, the heater  606  is an electric heater that operates on direct current power (e.g., 12 VDC power). The compliant member  608  can be formed of a suitable material and may comprise a spring. In the particular example provided, the compliant member  608  is formed of an elastomer that additionally seals the joint between the output member  602  and the actuator housing  600 . 
     In an unactuated condition (shown in  FIG. 28 ), the phase change material  604  is distributed about the compliant member  608  and the compliant member  608  biases the output member  602  into a returned position in which the output member  602  is substantially housed in the actuator housing  600 . The heater  606  can be activated to cause the phase change material  604  to change into a phase in which the phase change material  604  has a larger volume, which increases the pressure within the actuator housing  600 . In response to the increase in pressure, the compliant member  608  can deform, which permits the output member  602  to be urged outwardly of the actuator housing  600  as shown in  FIG. 29  to permit the brake shoe  144 n to contact the rotor surface  160 n of the brake rotor  152 n. It will be appreciated that after the operation of the heater  606  has been halted and the phase change material  604  begins to revert to its other phase (having reduced volume), the compliant member  608  can push the phase change material  604  radially outwardly, which can permit the compliant member  608  to pull the output member  602  back into the actuator housing  600 . 
     While the previous example has been described as including a heater, it should be appreciated that other types of energy may be employed to change the phase of the phase change material  604 . For example, heat from an internal combustion engine could be transmitted through the actuator housing  600  to the phase change material  604  to initiate a change in the phase of the phase change material  604 . Additionally or alternatively, while the linear motor of the previous example has been described as having a rod-in-cylinder configuration, it will be appreciated that the linear motor could be configured differently. For example, the linear motor could have an annular configuration, similar to the annular cylinder  200  shown in  FIG. 8 . 
     A portion of another driven device constructed in accordance with the teachings of the present disclosure is illustrated in  FIG. 30 . In this example, the actuator is similar to that which is shown in  FIGS. 15-21 , except a worm drive is employed in lieu of the linear motor and linkage. In this regard, the drum actuator  302 p can comprise a worm gear or wheel  650  that is driven by a worm screw  652 , which in turn can be driven by a motor  654  having a rotary output. 
     With reference to  FIG. 31 , a portion of another driven accessory constructed in accordance is illustrated. The clutched driven device  10 r can be generally similar to that which is illustrated in  FIG. 8 , except that the actuator  60 r includes a device  700 , which has a magnetorheological fluid or an electrorheological fluid, in lieu of a linear motor. The device  700  can include a housing  702 , a stationary member  704 , a fluid  706 , one or more seals  708 , and a means for affecting a viscosity of the fluid  706 . The brake rotor  152 r can be received in the housing  702  opposite the stationary member  704 . The housing  702  can be non-rotatably coupled to an appropriate structure, such as the housing of the water pump assembly  20  ( FIG. 1 ). The fluid  706  can be received in the housing  702  and can be disposed between the brake rotor  152 r and the stationary member  704 . The stationary member  704  can be coupled to an appropriate structure such that it is disposed in a non-rotating condition. If desired, the stationary member  704  can be integrally formed with the housing  702 . The seals  708  can seal the housing  702  to the brake rotor  152 r and the stationary member  704 . The viscosity affecting means  710  can comprise any means that causes the fluid  706  to change its viscosity. For example, if the fluid  706  is a magnetorheological fluid, the viscosity affecting means  710  can comprise a wire coil  712  that can be configured to generate a magnetic field that is suited to change the viscosity of the fluid  706 . If the fluid  706  was an electrorheological fluid, the viscosity affecting means  710  could comprise a power supply that was configured to selectively apply power to fluid  706  to cause the fluid  706  to change its viscosity. It will be appreciated that the fluid  706  has a normal condition having a first viscosity that permits the brake rotor  152 r to rotate in the fluid  706  without generating a significant amount of drag (i.e., so that rotary power is transmitted through the clutch assembly  16 r). Operation of the viscosity affecting means  710  can cause the viscosity of the fluid  706  to change such that the fluid  706  resists rotation of the brake rotor  152 r to thereby create a drag force that is imparted to the brake rotor  152 r and which causes the coiling of the wrap spring  56  to inhibit the transmission of rotary power through the clutch assembly  16 r. 
     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.