Patent Publication Number: US-2022220885-A1

Title: Clutched pulley assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 62/846,217 filed May 10, 2019, and to U.S. provisional application No. 62/952,890, filed Dec. 23, 2019, the contents of both of which are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Some mild hybrid vehicles increase fuel efficiency by shutting off the internal combustion engine when the vehicle comes to a standstill, for example, when stopped at a traffic light. In such vehicles a motor-generator unit (MGU) employed in the engine accessory drive system can be used use to restart the engine. The problem with such systems is that the air conditioning compressor or other accessory drive system load is also shut down while the engine is off, which then necessitates a trade-off between passenger comfort and fuel efficiency. It is possible to avoid this problem by using electrically powered air conditioning compressors or other such electrically powered loads, but such devices require an additional electric motor and inverter which adds considerable cost and complexity. It would be beneficial to have an accessory drive system where the engine powers a conventional mechanical air conditioning compressor most of the time, but when the engine turns off, the MGU powers the conventional mechanical air conditioning compressor or other such load. This could be achieved by a clutched pulley or pulley assembly. 
     There are also other potential applications for a clutched pulley or pulley assembly in an accessory drive system or other endless drive systems where it is desired to selectively or dynamically power (or not power) the accessories or other loads. 
     A clutched pulley or pulley assembly for an accessory drive system is thus desired. 
     SUMMARY 
     In a first aspect, a pulley assembly is provided for an accessory drive system of an internal combustion engine. The pulley assembly includes a first rotary drive member, a second rotary drive member, a slider gear, and an actuator. The first rotary drive member is configured to be rotatably supported on a shaft of a rotary power device, such as the shaft of a motor-generator unit (MGU) or crankshaft. The first rotary drive member is rotatable about a rotational axis, the rotation being independent of the rotation of the shaft when the first rotary drive member mounted thereon. The first rotary drive member, which may be a sheave, has a first set of spline teeth thereon. The second rotary drive member is configured to be fixed to the shaft so as to rotate therewith about the rotational axis when fixed on the shaft. The second rotary drive member, which may also be a sheave, has a second set of spline teeth thereon. The slider gear is disposed for rotation about the rotational axis, and includes a set of slider gear spline teeth thereon. The slider gear is axially moveable between a torque cut-off position and a torque transfer position. In the torque cut-off position the slider gear spline teeth intermesh with the spline teeth of one of the first and second rotary drive members but not the other of the first and second rotary drive members, thereby operatively disconnecting the first and second rotary drive members from each other. In the torque transfer position the slider gear spline teeth simultaneously intermesh with the spline teeth of both the first and second rotary drive members, thereby operatively connecting the first and second rotary drive member to each other. The actuator, which is mountable to the rotary power device, is connected to the slider gear to drive the slider gear axially to between the torque transfer position and the torque cut-off position. 
     The first rotary drive member can be mounted on a bearing configured to be mounted to the shaft so that the first rotary drive member is independently rotatable relative to the shaft. 
     The slider gear can have at least one slider gear wedge member and the other of the first and second rotary drive members can have at least one wedge member that is shaped complimentarily to the shape of the slider gear wedge member so that movement of the slider gear to the torque transfer position brings the at least one slider gear wedge member into sliding engagement with the at least one wedge member of the other of the first and second rotary drive members, and in the process of such engagement, a first side of the slider gear spline teeth becomes wedged against a first side of the spline teeth of the other of the first and second rotary drive members. This structure aids in reducing the noise while engaged. 
     The actuator can include a bias spring for urging the slider gear towards the torque transfer position. 
     The actuator can include a plunger ring concentrically mounted about the shaft, wherein the plunger ring has at least one leg extending in an axial direction, and wherein the other of the first and second rotary drive members includes at least one axial passageway in which the at least one leg is disposed. The plunger ring can thus be axially slidable relative to the other of the first and second rotary drive members so as to drivingly engage the slider gear. A driver screw can be concentrically mounted about the shaft for independent rotation relative to the shaft and a nut driver can be concentrically mounted about the shaft and operatively connected to the driver screw, the nut driver being constrained from rotation so as to translate axially when the driver screw rotates and engage the plunger ring. Various means are described for rotating the driver screw. 
     In a second aspect, an accessory drive system for an internal combustion engine is provided. The system includes a crankshaft pulley mounted to an engine crankshaft; a compressor pulley mounted to a compressor shaft; a pulley assembly mounted to a motor-generator unit (MGU) shaft; and first and second endless drive members. The pulley assembly includes: a first sheave rotatably mounted via a bearing to the MGU shaft so as to be rotatable independent of the MGU shaft, wherein the first sheave has a first set of spline teeth thereon; a second sheave fixed to the MGU shaft so as to rotate therewith, wherein the second sheave has a second set of spline teeth thereon; a slider gear disposed for rotation about the MGU shaft, wherein the slider gear has a set of slider gear spline teeth thereon and the slider gear is axially moveable between a torque cut-off position and a torque transfer position, wherein, in the torque cut-off position the slider gear spline teeth intermesh with the second sheave spline teeth but not the first sheave spline teeth, thereby operatively disconnecting the first and second sheaves from each other, and wherein, in the torque transfer position the slider gear spline teeth simultaneously intermesh with the second sheave spline teeth and the first sheave spline teeth, thereby operatively connecting the first and second sheaves to each other; and an actuator, mountable to an MGU, and connected to the slider gear to drive the slider gear axially between the torque transfer position and the torque cut-off position. The first endless drive member interconnects the crankshaft pulley and the first sheave and the second endless drive member interconnects the compressor pulley and the second sheave. 
     In the second aspect, the slider gear can have at least one slider gear wedge member and the first sheave can have at least one wedge member that is shaped complimentarily to the shape of the slider gear wedge member such that movement of the slider gear to the torque transfer position brings the at least one slider gear wedge member into sliding engagement with the at least one first sheave wedge member, and in the process of such engagement, a first side of the slider gear spline teeth becomes wedged against a first side of the first sheave spline teeth. This structure aids in reducing noise while engaged. 
     In the second aspect, the actuator can include: a bias spring for urging the slider gear towards the torque transfer position; a plunger ring concentrically mounted about the MGU shaft, the plunger ring including at least one leg extending in an axial direction, wherein the first sheave includes at least one axial passageway in which the at least one leg is disposed, the plunger ring being axially slidable relative to the first sheave so as to drivingly engage the slider gear; a driver screw concentrically mounted about the MGU shaft for independent rotation relative to the MGU shaft; a nut driver concentrically mounted about the MGU shaft and operatively connected to the driver screw, the nut driver being constrained from rotation so as to translate axially when the driver screw rotates and engage the plunger ring; and means for rotating the driver screw. 
     In the second aspect, the system can include a compressor and an MGU. The MGU can be operated at a rotational speed substantially equivalent to the rotational speed of the crankshaft immediately prior to changing the position of the slider gear, wherein equivalency should be understood taking into account different pulley ratios. Alternatively, the accessory drive system can be operated in a stand cooling mode in which the slider gear is positioned in the torque cut-off position, the engine is not operating and the crankshaft pulley is not rotating, and the MGU operates to power the compressor via the second endless drive member. Alternatively, the accessory drive system can be operated in an enhanced cooling mode in which the engine is operating at idle and the crankshaft pulley is rotating at idle speed, the slider gear is positioned in the torque cut-off position, and the MGU operates to power the compressor via the second endless drive member at a higher rotational speed that would have been available if the engine was powering the compressor. 
     In a third aspect, an accessory drive system for an internal combustion engine is provided. The accessory drive system includes an MGU pulley mounted to the shaft of a motor-generator (MGU) unit; a compressor pulley mounted to a compressor shaft; a pulley assembly mounted to a crankshaft of an engine; and a endless drive member. The pulley assembly includes: a sheave rotatably mounted via a bearing to the crankshaft so as to be rotatable independent of the crankshaft, the sheave having a first set of spline teeth thereon; a rotary drive member fixed to the crankshaft so as to rotate therewith, wherein the rotary drive member has a second set of spline teeth thereon; a slider gear disposed for rotation about the crankshaft, wherein the slider gear has a set of slider gear spline teeth thereon and the slider gear is axially moveable between a torque cut-off position and a torque transfer position, wherein, in the torque cut-off position the slider gear spline teeth intermesh with the rotary drive member spline teeth but not the sheave spline teeth, thereby operatively disconnecting the sheave and the rotary drive member from each other, and wherein, in the torque transfer position the slider gear spline teeth simultaneously intermesh with the rotary drive member spline teeth and the sheave spline teeth, thereby operatively connecting the rotary drive member and the sheave to each other, and an actuator connected to the slider gear to drive the slider gear axially between the torque transfer position and the torque cut-off position. The endless drive member interconnects the sheave, the MGU pulley and the compressor pulley. 
     In the third aspect, the slider gear can have at least one slider gear wedge member and the sheave can have at least one wedge member that is shaped complimentarily to the shape of the slider gear wedge member such that movement of the slider gear to the torque transfer position brings the at least one slider gear wedge member into sliding engagement with the at least one sheave wedge member, and in the process of such engagement, a first side of the slider gear spline teeth becomes wedged against a first side of the sheave spline teeth. This structure aids in reducing noise while engaged. 
     In the third aspect, the actuator can include: a bias spring for urging the slider gear towards the torque transfer position; a plunger ring concentrically mounted about the crankshaft, the plunger ring including at least one leg extending in an axial direction, wherein the sheave includes at least one axial passageway in which the at least one leg is disposed, the plunger ring being axially slidable relative to the sheave so as to drivingly engage the slider gear; a driver screw concentrically mounted about the crankshaft for independent rotation relative to the crankshaft; a nut driver concentrically mounted about the crankshaft and operatively connected to the driver screw, the nut driver being constrained from rotation so as to translate axially when the driver screw rotates and engage the plunger ring; and means for rotating the driver screw. 
     The actuator of any of the 1 st  to 3 rd  aspects can include a rotary motor coupled to a worm gear, which drives a sector gear connected to the driver screw. The worm gear can be packaged underneath, as opposed to inline with, the rotary motor such that a worm gear rotational axis lies parallel to the motor rotational axis. A gear box can be provided to facilitate such an axis-shifting arrangement. This actuator is able to provide rapid actuation of the slider gear and is advantageous from a packaging point of view. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The foregoing and other aspects of the invention will be better understood with reference to the attached drawings, wherein: 
         FIG. 1  is a perspective view of an accessory drive system for an internal combustion engine; 
         FIG. 2  is a perspective view of a motor-generator unit (MGU) employed in the accessory drive system shown in  FIG. 1 ; 
         FIG. 3A  is perspective cross-sectional view of an MGU pulley assembly having an integrated clutch mechanism, wherein the integrated clutch mechanism is shown in an engaged or torque transfer position; 
         FIG. 3B  is perspective cross-sectional view of the MGU pulley assembly, wherein the integrated clutch mechanism is shown in a disengaged or torque cut-off position; 
         FIG. 4  (comprising  FIGS. 4A-4E ) is an exploded view of the MGU pulley assembly; 
         FIG. 5  (comprising  FIGS. 5A-5E ) is an exploded view of the MGU pulley assembly taken from a viewpoint opposite to the viewpoint shown in  FIG. 4 ; 
         FIGS. 6A and 6B  are detail plan views of gear engagement profiles in the MGU pulley assembly when it is in the engaged and disengaged positions, respectively; 
         FIG. 7  is an exploded view of an actuator employed in the MGU pulley assembly shown in  FIGS. 3-5 ; 
         FIG. 8  is an exploded view of an alternative actuator that can be utilized in the MGU pulley assembly; 
         FIG. 9  is a partial assembly view of the alternative actuator shown in  FIG. 8 ; 
         FIG. 10  is a front view of the alternative actuator shown in  FIG. 8 ; 
         FIG. 11  is a side view of the alternative actuator shown in  FIG. 8 ; 
         FIG. 12  is a graph showing rotational speeds of various components of the accessory drive system as the MGU pulley assembly integrated clutch mechanism changes state to vary operating modes of the accessory drive system; and 
         FIGS. 13A and 13B  are cross-sectional views of a crankshaft pulley assembly having an integrated clutch mechanism similar to that shown in  FIGS. 3-5 , wherein  FIG. 13A  depicts the integrated clutch mechanism in an engaged or torque transfer position and  FIG. 13B  depicts the integrated clutch mechanism in an disengaged or torque cut-off position. 
     
    
    
     DETAILED DESCRIPTION 
     For simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiment or embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. It should be understood at the outset that, although exemplary embodiments are illustrated in the drawings and described below, the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques illustrated in the drawings and described below. 
     Various terms used throughout the present description may be read and understood as follows, unless the context indicates otherwise: “or” as used throughout is inclusive, as though written “and/or”; singular articles and pronouns as used throughout include their plural forms, and vice versa; similarly, gendered pronouns include their counterpart pronouns so that pronouns should not be understood as limiting anything described herein to use, implementation, performance, etc. by a single gender; “exemplary” should be understood as “illustrative” or “exemplifying” and not necessarily as “preferred” over other embodiments. Further definitions for terms may be set out herein; these may apply to prior and subsequent instances of those terms, as will be understood from a reading of the present description. 
     Modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein without departing from the scope of the disclosure. For example, the components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components and the methods described may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. As used in this document, “each” refers to each member of a set or each member of a subset of a set. 
       FIG. 1  shows an accessory drive system  10  for an internal combustion engine (or “ICE”), partially shown at reference numeral  12 . The system  10  includes the ICE  12 , a motor-generator unit (or “MGU”)  14  (alternatively referred to as a belt starter-generator or “BSG”), and at least one accessory such as an air conditioning compressor (“AC”) unit  16 . Each of these elements  12 ,  14 ,  16  includes a rotary drive member: the ICE  12  features a crankshaft (or “CS”) pulley  18  that receives (or delivers) rotational power from (to) the ICE  12 ; the MGU  14  includes an MGU pulley assembly  20  that is drivingly connected to an internal MGU shaft  30  (see  FIGS. 3-5 ); and the AC unit  16  includes an AC pulley  22  that is drivingly connected to an internal shaft of the AC unit  16  (not explicitly shown in  FIG. 1 ). The CS pulley  18  and the MGU pulley assembly  20  are inter-connected via a first endless drive member such as poly-V belt  24 A, and the MGU pulley assembly  20  and AC pulley  22  are inter-connected via a second endless drive member such as poly-V belt  24 B. 
       FIG. 2  shows the MGU  14  in isolation, with MGU pulley assembly  20  mounted on the MGU shaft. The MGU  14  per se is a conventional product. The MGU pulley assembly  20  is novel and features two pulley sheaves  26 ,  28  that can be selectively operatively connected or disconnected to/from one another via an integrated clutch mechanism discussed below. In the illustrated embodiment, the sheave  26  is connected to the CS pulley  18  via the belt  24 A (and thus may be referred to herein as the “CS sheave”) and the sheave  28  is connected to the at least one accessory such as the AC unit  16  via the belt  24 B (and thus may be referred to herein as the “AC sheave”). In the illustrated embodiment the AC sheave  28  is fixed to the MGU shaft  30  (see  FIGS. 3-5 ) and the CS sheave  26  is rotatably mounted, e.g. via a bearing, to the MGU shaft  30 . 
     With such capability, the at least one accessory such as the AC unit  16  can be powered by either the ICE  12  or the MGU  14 . 
     When the CS sheave  26  is operatively connected to the AC sheave  28 , the belt  24 A can transfer rotational power between the ICE CS pulley  18  and the CS sheave  26 , which transfers rotational power via the integrated clutch mechanism to the AC sheave  28 , which transfers rotational power via the belt  24 B to the AC pulley  22  and the AC unit  16 . In a hybrid vehicle which uses the accessory drive system  10  and the MGU  14  for multiple functions, this configuration can be used for:
         a ‘normal’ mode, wherein rotational power from the ICE  12  and CS pulley  18  is used to operate the MGU  14  as a generator to recharge a battery (not shown) and power the AC unit  16 ;   a ‘hybrid start’ mode, wherein the ICE  12  is shut off and rotational power from the MGU  14  is used to turn the CS pulley  18  and start the ICE  12 , in which case the AC unit  16  is powered by the MGU  14 ;   a ‘boost’ mode, wherein rotational power from the MGU  14  is used to turn the CS pulley  18  to increase torque on the ICE crankshaft in order to assist in driving the vehicle, in which case the AC unit  16  is powered by the MGU  14 ; and/or   a ‘regen’ mode, wherein, rotational power from the CS pulley  18  arising from vehicle momentum is used to operate the MGU  14  as a generator to recharge a battery (not shown) and power the AC unit  16 .       

     When the CS sheave  26  is operatively disconnected from the AC sheave  28 , the CS sheave  26  freewheels in that it is operatively disconnected from the MGU  14 . This configuration is particularly useful for a ‘stand-cooling’ mode, wherein the vehicle is at a standstill with the ICE  12  shut off but the at least one accessory such as the AC unit  16  is powered by the MGU  14 . This allows the vehicle to, for example, continue to keep providing passenger comfort with mechanically driven components that are less expensive than electrically driven accessories such as electric AC compressors. It should also be appreciated that if the CS sheave  26  is operatively disconnected from the AC sheave  28 , the vehicle may also be operated in an ‘enhanced cooling’ mode wherein the ICE  12  runs at idle but the AC unit  16  is powered by the MGU  14  at rotational speeds higher than would be available if the AC unit  16  was powered by the CS sheave  26  when the ICE  12  is at idle. 
     Referring additionally to the cross-sectional and exploded views of the MGU pulley assembly  20  in  FIGS. 3, 4 and 5 , the MGU internal shaft  30  is an integral part of the MGU  14 . The AC sheave  28  is fixedly mounted to the MGU shaft  30 . One structure for such mounting is shown in the illustrated embodiment wherein the AC sheave  28  has a toothed internal bore  32  that mates with a complimentarily toothed circumference  34  of the MGU shaft  30  to fix the two components together. A collar  31  can be fitted about an opposing end of the MGU shaft  30  and a liner or sleeve  33 , which provides a bearing surface as described in greater detail below, can be fitted over the MGU shaft  30  to locate the bore  32  on the MGU shaft  30 . The sleeve  33  can be press-fit into the bore  32 . The MGU shaft  30  can include a threaded bore  36  which receives a lock nut  38  for fastening the AC sheave  28  to the MGU shaft  30 , with washers  40  provided for load distribution. The collar  31 , sleeve  33 , toothed bore  32 , toothed circumference  34 , threaded bore  36 , and lock nut  38  enable the MGU pulley assembly  20  to be unitarily mounted to the MGU shaft  30 . 
     Alternative mounting structures are also possible. For example, the AC sheave  28  can be press fit directly onto the MGU shaft  30 . Also, instead of the sleeve  33 , a bearing can be press fit directly onto the MGU shaft  30  to journal the CS sheave  26  thereon. 
     The AC sheave  28  includes a circumferential power transfer surface such as provided by V-shaped grooves  42  that engage the poly-V belt  24 B. The AC sheave  28  also includes a radially orientated wall  44  disposed between the circumferential power transfer surface and circumferential wall defining the bore  32  such that, generally speaking, the AC sheave  28  defines an axially-orientated toroidal space  46  in which clutch components are disposed. 
     The CS sheave  26  includes a circumferential power transfer surface, such as provided by V-shaped grooves  52  that engage the poly-V belt  24 A. The CS sheave  26  includes a shaft or hub portion  54  that is rotatably mounted on the MGU shaft  30  via, for example, a needle roller bearing  57  which, in turn, is mounted on the shaft sleeve  33 . If desired the shaft sleeve can function as one of the roller bearing races. The hub portion  54  can be produced as a separate piece and fixed, e.g., by press fit, to a cylindrical body  56  featuring the circumferential power transfer surface or alternatively integrated with the cylindrical body  56 . A thrust washer  58  can be disposed axially between the hub portion  54  and the collar  31 . 
     The CS sheave  26  includes a series of circumferentially spaced, axially projecting, dog teeth  60 . The dog teeth  60  can be formed on an interior or axial edge wall of the cylindrical body  56 . Alternatively, as shown in the illustrated embodiment, the dog teeth  60  can be formed on an axial edge of a separately-produced wedge ring  62  (seen best in  FIGS. 4 &amp; 5 ) that also has an exterior wall with a series of circumferentially spaced, radially-outward projecting teeth  64  formed therein that are fixedly wedged into a complimentarily-shaped series of circumferentially spaced, axially orientated, radially-inward projecting splines  66  extending from an interior circumferential wall of the cylindrical body  56 . 
     The AC sheave  28  includes a series of circumferentially spaced, axially orientated, radially-inward projecting splines  70  formed on an interior wall thereof. The splines  70  can be formed unitarily in the AC sheave  28  or, as shown in the illustrated embodiment, the splines can be provided on an interior circumferential wall of a separately manufactured spline ring  68  that is fixed, e.g., by press fit, to the AC sheave  28 . 
     A slider gear  72  is interposed between the AC sheave  28  and CS sheave  26  in order to operatively connect or disconnect the sheaves  26 ,  28 . The slider gear  72  has an exterior circumferential wall on which a series of circumferentially spaced, axially orientated, radially-outward projecting splines  74  are formed. The splines  74  are shaped to complement the shape of the AC sheave splines  70  as well as the CS sheave splines  66 , with sufficient interstitial space between the complimentary splines to enable the slider gear  72  to slide axially relative to the AC sheave  28  and the CS sheave  26 . The slider gear  72  also includes an axial edge wall on which a series of circumferentially spaced, axially projecting dog teeth  76  are formed. These dog teeth  76  are shaped to complement the shape of the CS sheave dog teeth  60 . 
     The slider gear  72  is axially translatable between an engaged or torque transfer position and a disengaged or torque cut-off position. In the engaged or torque transfer position, as shown in  FIG. 3A , the slider gear splines  74  meshingly engage the AC sheave splines  70  as well as the CS sheave splines  66 , and the stroke is such that the slider gear dog teeth  76  intermesh with the CS sheave dog teeth  60 , thereby operatively connecting the AC sheave  28  and the CS sheave  26  to each other. In the disengaged or torque cut-off position, as shown in  FIG. 3B , the slider gear splines  74  and dog teeth  76  do not engage the CS sheave splines  66  and dog teeth  60 , respectively; the slider gear splines  74  meshingly engage only the AC sheave pulley splines  70 , and thus the AC sheave  28  and the CS sheave  26  are operatively disconnected from each other. In summary, the slider gear splines  74  continuously intermesh with the AC sheave splines  70  and the slider gear splines  74  and dog teeth  76  selectively or intermittingly intermesh the CS sheave splines  66  and dog teeth  60 . 
     In the foregoing manner, the MGU pulley assembly  20  incorporates an integrated clutch mechanism to selectively operatively connect or disconnect two sheaves mounted about the same shaft. 
     It will be appreciated that in alternative embodiments a reverse arrangement can be realized wherein the slider gear splines intermesh continuously with the CS sheave splines and selectively or intermittingly mesh with the AC sheave splines. In such an embodiment dog teeth can be formed on the opposite axial edge of the slider gear and dog teeth can be provided on the AC sheave for mating engagement with the slider gear dog teeth when the slider gear splines engage the AC sheave splines. 
     If desired, the dog teeth may be omitted entirely such that torque transfer occurs only through the sheaves&#39; splines. Alternatively, the splines on the CS sheave (or AC sheave in the alternative embodiment) may be omitted such that torque transfer occurs only through the dog teeth. 
     However, provisioning the splines  66 ,  70 ,  74  and dog teeth  60 ,  76  offers certain advantages in reducing noise of engagement and noise while engaged. Referring additionally to the detail plan view of  FIGS. 6A and 6B , it will be seen that each of the CS sheave dog teeth  60  are slanted relative to the axial direction and each of the slider gear dog teeth  76  are correspondingly slanted relative to the axial direction. The slider gear splines  74  have circumferential extents W 1  that are slightly smaller than circumferential extents W 2  of receiving slots  67  between the CS sheave splines  66 , i.e., there is some play between these elements. As the slider gear splines  74  enter the CS sheave receiving slots  67 , the complimentary slants of the slider gear dog teeth  76  and the CS sheave dog teeth  60  wedge the slider gear splines  74  against one side of the CS sheave splines  66 , which helps to reduce impact noise. Thus, the dog teeth  60  and  76  can be considered as wedge members, and it will be appreciated that a similar effect can be realized with at least one wedge member provisioned on the slider gear  72  and at least one complementary wedge member provisioned on the CS sheave  26 . By wedging the slider gear  72  against the CS sheave  26 , it is possible to reduce vibratory noise that arises from torsional vibrations present in the accessory drive system due to instantaneous torque variations transmitted by the crankshaft, which tend to induce a to and fro or vibratory motion between the slider gear  72  and the CS sheave  26 . 
     As shown in the illustrated embodiment, a plunger ring  77  can be slidably mounted to the CS sheave hub portion  54  to effect translation of the slider gear  72  between its engaged and disengaged positions. The hub portion  54  can feature a plurality of circumferentially spaced, axially orientated passageways  78  and the plunger ring  77  can have a corresponding plurality of axially extending legs  80  installed into respective passageways  78  for slidably mounting the plunger ring  77  to the hub portion  54 . O-ring seals  82  can be installed on the legs  80  to inhibit transfer of grease or dirt. A thrust washer  84  can be disposed between the plunger ring  77  and the slider gear  72 . A spring  85  can be disposed between the slider gear  72  and the AC sheave radially orientated wall  44  to bias the slider gear  72  to the engaged position. 
     The plunger ring  77  can be considered as a portion of an actuator which provides a means for translating the slider gear  72  between its engaged and disengaged positions. Referring additionally to the partial exploded view in  FIG. 7 , one example of an actuator  86  is shown in the illustrated embodiment. This actuator  86  includes a housing  88  mountable to the casing of the MGU  14 , for example, via mounting legs  90 . An actuator guide flange  92  having a radial plate portion  94  and an axial stub portion  96  is mounted to the housing via the plate portion  94 . The plate portion  94  is fitted on a raised lip  98  of the housing  88  so as to define an arcuate slot  100 . A driver screw  102  has a plate portion  104  slidably mounted in the arcuate slot  100 . The plate portion  104  has an arm  106  which extends from a window  108  formed in the lip  98  such that the driver screw  102  is rotatable over a limited rotational angle. The driver screw  102  has a threaded axial or screw portion  110  which meshes with a complimentarily threaded nut driver  112 . The nut driver  112  is splined on an exterior circumferential wall  114  and the guide flange axial stub portion  96  is complimentarily splined on an interior circumferential wall  116  so as to preclude rotation of the nut driver  112  and induce axial translation of the nut driver  112  when the driver screw  102  is rotated. 
     The driver screw  102  can be rotated by a linear actuator  120  coupled to the driver screw arm  106  by a linkage, for example, by a coupling  122 , pin  124 , and actuator arm  126 . 
     From the foregoing it will be seen that activating the linear actuator  120  in a first direction will rotate the driver screw  102 , which, in turn, causes the nut driver  112  to translate axially and push the plunger ring  77  and slider gear  72  axially to the engaged position, overcoming the bias force provided by the return spring  85 . Activating the linear actuator  120  in a second direction, opposite the first direction, causes the driver screw  102  to rotate in the opposite direction, which causes the nut driver  112  to translate axially in a reverse direction, allowing the return spring  85  to push the slider gear  72  and plunger ring  77  in the reverse direction to the disengaged position. 
     Another example of an actuator  130  is shown in  FIGS. 8-11 . This actuator  130  includes a bracket  132  mountable to the casing of the MGU  14 , for example, via mounting legs  134 . The bracket  132  has a circular opening  136 . A rear housing portion  138  is mounted to the bracket  132 . The rear housing portion includes a cylindrical projection  140  concentrically fitted into the circular opening  136 . A front housing portion  142  is also mounted to the bracket  132 . The front housing portion  142  has a circular opening  144  concentrically arranged about the circular opening  136 . A driver screw  146  is rotatably mounted about the cylindrical projection  140 . The driver screw  146  has a threaded axial or screw portion  148  which meshes with a complimentarily threaded nut driver  150 . The nut driver  150  is splined on an exterior circumferential wall  152  and the front housing portion  142  is complimentarily splined on an interior circumferential wall  154  that defines the circular opening  144  so as to preclude rotation of the nut driver  150  and induce axial translation of the nut driver  150  when the driver screw  146  is rotated. 
     In this actuator  130 , the driver screw  146  features a radial arm  156  that terminates with a sector gear  158 . The sector gear  158  is disposed in an arcuate slot  160  provided in the rear housing  138 , thus limiting angular travel of the driver screw  146 . The sector gear  158  meshes with a worm gear  162  that is rotatably disposed in an alignment collar  164  fixed to the bracket  132 . A motor  170  drives the worm gear  162  via a gear box  172  mounted to the bracket  132 . The gear box  172 , provisioned by container  172 A and cover  172 B, houses reduction gears  174 A,  174 B that are operatively connected to the motor  170  and worm gear  162 , respectively. For compact packaging arrangement, the worm gear  162  can be disposed underneath the motor  170  with the worm gear rotational axis lying parallel to the motor rotational axis and the reduction gears  174 A,  174 B being installed to facilitate such an axis-shifting arrangement. 
     A controller printed circuit board (PCB) can be installed between the front housing portion  142  and the bracket  132 . 
     From the foregoing it will be seen that activating the motor  170  in a first direction will drive the worm gear  162 , which drives the sector gear  158 , causing the driver screw  146  to rotate, which, in turn, causes the nut driver  150  to translate axially and push the plunger ring  77  and slider gear  72  axially to the engaged position. Activating the motor  170  in a second direction, opposite the first direction, causes the driver screw  146  to rotate in the opposite direction, which causes the nut driver  150  to translate axially in a reverse direction, allowing the return spring  85  to push the slider gear  72  and plunger ring  77  in the reverse direction to the disengaged position. 
     In typical operation, the actuation of the integrated clutch mechanism of the MGU pulley assembly  20  occurs when the rotational speed of the MGU  14  is minimal and preferably zero. Thus to change state from any of the normal, hybrid start, boost and/or regen modes to the stand cooling mode, or vice versa, the speed of the MGU  14  is preferably reduced to zero before the integrated clutch mechanism is actuated, the integrated clutch mechanism is actuated, and then the MGU  14  is returned to operating speed. An example of such a sequence is shown in  FIG. 12 , wherein plot  202  represents the rotational speed of the MGU  14 , plot  204  represents the rotational speed of the AC pulley  22 , and plot  206  represents the rotational speed of the CS pulley  18 . In state (1), the system  10  is in the stand cooling mode. In state (2), the MGU  14  speed is reduced to zero. In state (3) the integrated clutch mechanism is actuated, the slider gear  72  being actuated to the engaged or torque transfer position from the disengaged or torque cut-off position. This transition can occur in a short time frame; for example the actuator  130  can be constructed to effect the transition in under 150 milliseconds. In state (4) the system  10  is in the hybrid start mode. In state (5) the system  10  is in the normal (ICE on) mode. In state (6) the system  10  is in the regen mode, where the ICE  12  is shut down and the vehicle is brought to a standstill, at which point the MGU speed nears zero. In state (6) the integrated clutch mechanism is actuated, the slider gear  72  being actuated to the disengaged or torque cut-off position from the engaged or torque transfer position. In state (8) the system  10  returns to the stand cooling mode. 
     It should also be appreciated that it is not absolutely necessary to reduce the MGU speed to zero before actuating the integrated clutch mechanism of the MGU pulley assembly  20 . This could be beneficial in some situations, for example, to enter into the enhanced cooling mode without first stopping the ICE  12 . In such situations, a dynamic engagement or disengagement of the integrated clutch mechanism can be realized by equivalent speed (taking into account pulley ratios) and, optionally, torque matching. For dynamic disengagement, the MGU  14  can be operated to substantially equivalently match the rotational speed and torque of the ICE  12 , it being understood that the term “equivalent” means speeds that take into account any difference in diameter between the CS pulley  18  and the CS sheave  26 , as would be understood by those skilled in the art. This reduces the normal force on the splines  66 ,  70 ,  74  because torque transfer is reduced, and thus the frictional force acting on the slider gear  72  is reduced. Similarly, for dynamic engagement, the MGU  14  can be operated to substantially equivalently match the speed and the torque of the ICE  12 , it being understood that the term “equivalent” means speeds that take into account any difference in diameter between the CS pulley  18  and the CS sheave  26 . At this point the actuator  86  or  130  can retract, allowing the return spring  85  to push the slider gear  72  to engage with the CS sheave  26 . A small speed or torque delta in the boost direction will allow the slider gear splines  74  to seat fully in the CS sheave spline receiving slots  67 . 
     In an alternative embodiment, shown in  FIGS. 13A and 13B , a CS pulley assembly  18 ′ can integrate a clutch mechanism of the type described above. In this embodiment, the CS pulley assembly  18 ′ has a first rotary drive member  26 ′ with an endless drive member power transmitting surface such as V-shaped grooves  52  and a second rotary drive member  28 ′ that does not require an endless drive member power transmitting surface. The internal components of the CS pulley  18 ′ are substantially the same as the MGU pulley assembly  20  and thus like parts bear like reference numerals. In this embodiment, however, the first and second rotary drive members  26 ′ and  28 ′ are supported on a crankshaft shaft  30 ′ instead of the MGU shaft  30 . For the normal, hybrid start, boost and/or regen modes the slider gear  72  can be disposed in the engaged or torque transfer position, as seen in  FIG. 13A , so that the first and second rotary drive member  26 ′ and  28 ′ are operatively connected to each other. For the stand cooling mode, the slider gear  72  can be disposed in the disengaged or torque cut-off position, as seen in  FIG. 13B , so that the first and second rotary drive members  26 ′ and  28 ′ are operatively disconnected from each other. It will be appreciated that in an accessory drive system utilizing the CS pulley assembly  18 ′ a single endless drive member such as a poly-V belt can be deployed to interconnect the first rotary drive member  26 ′, a single pulley (not shown) connected to the MGU shaft  30 , and the AC pulley  22 . 
     While the endless drive members are shown herein as asynchronous poly-V belts, the endless drive members can be any other type of asynchronous or synchronous rotary power transmitting member. For example, another type of asynchronous rotary power transmitting member is a flat belt. Examples of synchronous rotary power transmitting members include timing belts or chains. In these alternative cases the sheaves as shown herein would replaced with the complimentary rotary drive members such as sprockets or gears. The term “rotary drive member” is thus intended to include a pulley, sheave, sprocket, or gear that interacts with an endless drive member or an intermediate rotary member that is rotatingly driven by a shaft. 
     In addition, while the driven accessory shown and discussed above has been the air conditioning compressor, it will be appreciated that the driven accessory can be another unit, for example, a compressor for a heat pump. 
     Those skilled in the art will appreciate that the embodiments disclosed herein can be modified or adapted in various other ways whilst still keeping within the scope of the appended claims. 
     
       
         
           
               
             
               
                   
               
               
                 Parts List 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 10 
                 accessory drive system 
               
               
                 12 
                 ICE 
               
               
                 14 
                 MGU 
               
               
                 16 
                 AC Unit 
               
               
                 18 
                 CS pulley 
               
               
                 20 
                 MGU pulley assembly 
               
               
                 22 
                 AC pulley 
               
               
                 24A, 24B 
                 belt 
               
               
                 26 
                 CS sheave 
               
               
                 28 
                 AC sheave 
               
               
                 30 
                 MGU shaft 
               
               
                 31 
                 collar 
               
               
                 32 
                 AC sheave, toothed bore 
               
               
                 33 
                 shaft sleeve 
               
               
                 34 
                 MGU shaft toothed circumference 
               
               
                 36 
                 MGU shaft, threaded bore 
               
               
                 38 
                 lock nut 
               
               
                 40 
                 washers 
               
               
                 42 
                 AC sheave, V-shaped grooves 
               
               
                 44 
                 AC sheave, radially orientated wall 
               
               
                 46 
                 AC Sheave, toroidal space 
               
               
                 52 
                 CS sheave, V-shaped grooves 
               
               
                 54 
                 CS sheave, hub portion 
               
               
                 56 
                 cylindrical body 
               
               
                 57 
                 roller bearing 
               
               
                 58 
                 thrust washer 
               
               
                 60 
                 CS sheave, dog teeth 
               
               
                 62 
                 wedge ring 
               
               
                 64 
                 wedge ring teeth 
               
               
                 66 
                 CS sheave splines 
               
               
                 67 
                 CS sheave, spline receiving slots 
               
               
                 68 
                 spline ring 
               
               
                 70 
                 splines 
               
               
                 72 
                 slider gear 
               
               
                 74 
                 slider gear spines 
               
               
                 76 
                 slider gear dog teeth 
               
               
                 77 
                 plunger ring 
               
               
                 78 
                 axially orientated passageways 
               
               
                 80 
                 plunger ring legs 
               
               
                 82 
                 O-rings 
               
               
                 84 
                 thrust washer 
               
               
                 85 
                 spring 
               
               
                 86 
                 actuator 
               
               
                 88 
                 housing 
               
               
                 90 
                 mounting legs 
               
               
                 92 
                 actuator guide flange 
               
               
                 94 
                 actuator guide flange, radial plate portion 
               
               
                 96 
                 actuator guide flange, axial stub portion 
               
               
                 98 
                 housing, raised lip 
               
               
                 100  
                 arcuate slot 
               
               
                 102  
                 driver screw 
               
               
                 104  
                 driver screw plate portion 
               
               
                 106  
                 driver screw arm 
               
               
                 108  
                 window 
               
               
                 110  
                 driver screw, screw portion 
               
               
                 112  
                 nut driver 
               
               
                 114  
                 nut driver exterior circumferential wall 
               
               
                 116  
                 guide flange axial stub portion interior circumferential wall 
               
               
                 120  
                 linear actuator 
               
               
                 122  
                 coupling 
               
               
                 124  
                 pin 
               
               
                 126  
                 actuator arm 
               
               
                 130  
                 actuator 
               
               
                 132  
                 bracket 
               
               
                 134  
                 mounting legs 
               
               
                 136  
                 bracket circular opening 
               
               
                 138  
                 rear housing portion 
               
               
                 140  
                 rear housing portion cylindrical projection 
               
               
                 142  
                 front housing portion 
               
               
                 144  
                 front housing portion circular opening 
               
               
                 146  
                 driver screw 
               
               
                 148  
                 driver screw threaded axial or screw portion 
               
               
                 150  
                 nut driver 
               
               
                 152  
                 nut driver exterior circumferential wall 
               
               
                 154  
                 front housing portion interior circumferential wall 
               
               
                 156  
                 driver screw radial arm 
               
               
                 158  
                 sector gear 
               
               
                 160  
                 rear housing arcuate slot 
               
               
                 162  
                 worm gear 
               
               
                 164  
                 alignment collar 
               
               
                 170  
                 motor 
               
               
                 172  
                 gear box 
               
               
                 174A, 174B 
                 reduction gears 
               
               
                 176  
                 controller printed circuit board 
               
               
                     18′ 
                 CS pulley assembly 
               
               
                     26′ 
                 first rotary drive member 
               
               
                     28′ 
                 second rotary drive member 
               
               
                     30′ 
                 crankshaft shaft