Patent Publication Number: US-9899132-B2

Title: Magnetically latching two position actuator and a clutched device having a magnetically latching two position actuator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/606,096 filed on Jan. 27, 2015. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to a magnetically latching two position actuator and a clutched device having a magnetically latching two position actuator. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Clutched devices, such as power transmitting devices, transmissions, or suspension components for example, often require linear motion to translate one or more power transmitting elements, such as friction plates or shift forks for example, into or out of engagement positions. These engagement positions can selectively connect or disconnect a vehicle axle, such as switching between two and four-wheel (or all-wheel) drive modes for example. The engagement positions can alternatively switch between transmission gears, such as between low and high speed gear ratios for example, or can electronically disconnect suspension components, such as sway bars for example. Various types of linear actuators exist to create such linear motion, such as hydraulic rams, rack and pinion gearing, or solenoids for example. However, there remains a need in the art for an improved actuator for providing linear motion in clutched devices. 
     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. 
     The present teachings provide for an actuator including a housing, a core assembly, a first electromagnet, and a second electromagnet. The housing can have a first pole piece, a second pole piece, and a central pole piece disposed between the first and second pole pieces. The central pole piece can have a central body and a bridge. The bridge can have a first base, a second base, and a span that extends between the first and second bases. The core assembly can be received in the housing and can be movable along a first axis between a first core position and a second core position. The core assembly can include a permanent magnet, and first and second cores coupled for common axial movement with the permanent magnet and spaced axially apart by the permanent magnet. The first and second electromagnet can be spaced axially apart by the central pole piece and can have opposite polarities. The central pole piece can extend radially inward of an outermost portion of the first core and radially inward of an outer most portion of the second core. The central body can be axially between the first and second electromagnets. The first base can be radially inward of the first electromagnet and can axially overlap with a portion of the first electromagnet. The second base can be radially inward of the second electromagnet and can axially overlap with a portion of the second electromagnet. 
     The present teachings provide for an actuator including a housing, a core assembly, a first electromagnet and a second electromagnet. The housing can have a first pole piece, a second pole piece, and a central pole piece that can be disposed between the first and second pole pieces. The central pole piece can have a central body and a bridge. The bridge can be disposed between the first and second pole pieces and axially movable relative thereto. The core assembly can be received in the housing. The core assembly can be movable along a first axis between a first core position and a second core position. The core assembly can include a permanent magnet, a first core, and a second core. The first and second cores can be coupled to the permanent magnet for common axial movement. The first and second electromagnets can be spaced axially apart by the central body and can have opposite polarities. 
     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. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a schematic of a motor vehicle having a disconnectable all-wheel drive system with a clutched device constructed in accordance with the teachings of the present disclosure; 
         FIG. 2  is a schematic illustration of a portion of the motor vehicle of  FIG. 1 , illustrating the clutched device in more detail; 
         FIG. 3  is a cross-sectional view of a portion of the clutched device of  FIG. 1 , illustrating an actuator of the clutched device of a first construction in more detail; 
         FIG. 4  is a cross-sectional view of the portion of the clutched device of  FIG. 3 , illustrating a plunger of the actuator in a first actuator position and an electromagnet of the actuator in an energized state; 
         FIG. 5  is a cross-sectional view of the portion of the clutched device of  FIG. 4 , illustrating the plunger in a second actuator position and the electromagnet in an un-energized state; 
         FIG. 6  is a cross-sectional view of a portion of the clutched device of  FIG. 1 , illustrating an actuator of the clutched device of a second construction in more detail; 
         FIG. 7  is a cross-sectional view of the portion of the clutched device of  FIG. 6 , illustrating a plunger of the actuator in a second actuator position and an electromagnet of the actuator in an un-energized state; and 
         FIG. 8  is a cross-sectional view of a portion of the clutched device of  FIG. 1 , illustrating an actuator of the clutched device of a third construction in more detail. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     With reference to  FIGS. 1 and 2  of the drawings, a motor vehicle constructed in accordance with the teachings of the present disclosure is schematically shown and generally indicated by reference numeral  10 . The vehicle  10  can include a powertrain  14  and a drivetrain  18  that can include a primary driveline  22 , a clutched device or power switching mechanism  26 , a secondary driveline  30 , and a control system  34 . In the various aspects of the present teachings, the primary driveline  22  can be a front driveline while the secondary driveline  30  can be a rear driveline. 
     The powertrain  14  can include a prime mover  38 , such as an internal combustion engine or an electric motor, and a transmission  42  which can be any type of ratio-changing mechanism, such as a manual, automatic, or continuously variable transmission. The prime mover  38  is operable to provide rotary power to the primary driveline  22  and the power switching mechanism  26 . 
     The primary driveline  22  can include a primary or first differential  46  having an input member  50  driven by an output member (not shown) of the transmission  42 . In the particular example shown, the first differential  46  is configured as part of the transmission  42 , a type commonly referred to as a transaxle and typically used in front-wheel drive vehicles. The primary driveline  22  can further include a pair of first axleshafts  54 L,  54 R that can couple output components of the first differential  46  to a set of first vehicle wheels  58 L,  58 R. The first differential  46  can include a first differential case  62  that is rotatably driven by the input member  50 , at least one pair of first pinion gears  66  rotatably driven by the first differential case  62 , and a pair of first side gears  70 . Each of the first side gears  70  can be meshed with the first pinion gears  66  and drivingly coupled to an associated one of the first axleshafts  54 L,  54 R. 
     The power switching mechanism  26 , hereinafter referred to as a power take-off unit (“PTU”), can generally include a housing  74 , an input  78  coupled for common rotation with the first differential case  62  of the first differential  46 , an output  82 , a transfer gear assembly  86 , a disconnect mechanism  90 , and a disconnect actuator  94 . The input  78  can include a tubular input shaft  98  rotatably supported by the housing  74  and which concentrically surrounds a portion of the first axleshaft  54 R. A first end of the input shaft  98  can be coupled for rotation with the first differential case  62 . The output  82  can include an output pinion shaft  102  rotatably supported by the housing  74  and having a pinion gear  106 . The transfer gear assembly  86  can include a hollow transfer shaft  110 , a helical gearset  114 , and a hypoid gear  118  that is meshed with the pinion gear  106 . The transfer shaft  110  concentrically surrounds a portion of the first axleshaft  54 R and is rotatably supported by the housing  74 . The helical gearset  114  can include a first helical gear  122  fixed for rotation with the transfer shaft  110  and a second helical gear  126  which is meshed with the first helical gear  122 . The second helical gear  126  and the hypoid gear  118  are integrally formed on, or fixed for common rotation with, a stub shaft  130  that is rotatably supported in the housing  74 . 
     The disconnect mechanism  90  can comprise any type of clutch, disconnect or coupling device that can be employed to selectively transmit rotary power from the primary driveline  22  to the secondary driveline  30 . In the particular example provided, the disconnect mechanism  90  comprises a clutch having a set of external spline teeth  134 , which can be formed on a second end of the input shaft  98 , a set of external clutch teeth  138 , which can be formed on the transfer shaft  110 , a mode collar  142  having internal spline teeth  146  constantly meshed with the external spline teeth  134  on the input shaft  98 , and a shift fork  150  operable to axially translate the shift collar  142  between a first mode position and a second mode position. It will be appreciated that the clutch could include a synchronizer if such a configuration is desired. 
     The mode collar  142  is shown in  FIG. 2  in its first mode position, identified by a “2WD” leadline, wherein the internal spline teeth  146  on the mode collar  142  are disengaged from the external clutch teeth  138  on the transfer shaft  110 . As such, the input shaft  98  is disconnected from driven engagement with the transfer shaft  110 . Thus, no rotary power is transmitted from the powertrain  14  to the transfer gear assembly  86  and the output pinion shaft  102  of the power take-off unit  26 . With the mode collar  142  in its second mode position, identified by an “AWD” leadline, its internal spline teeth  146  are engaged with both the external spline teeth  134  on the input shaft  98  and the external clutch teeth  138  on the transfer shaft  110 . Accordingly, the mode collar  142  establishes a drive connection between the input shaft  98  and the transfer shaft  110  such that rotary power from the powertrain  14  is transmitted through the power take-off unit  26  to the output pinion shaft  102 . The output pinion shaft  102  is coupled via a propshaft  154  to the secondary driveline  30 . The disconnect actuator  94  can include a housing  156  and a plunger  158  that is operable for axially, or linearly moving the shift fork  150  which, in turn, causes concurrent axial translation of the mode collar  142  between the first and second mode positions. The disconnect actuator  94  is shown mounted to the housing  74  of the PTU  26 . The disconnect actuator  94  can be a power-operated mechanism that can receive control signals from the control system  34 . The disconnect actuator  94  will be discussed in greater detail below, with regard to  FIGS. 3-5 . 
     The secondary driveline  30  can include the propshaft  154 , a rear drive module (“RDM”)  162 , a pair of second axleshafts  166 L,  166 R, and a set of second vehicle wheels  170 L,  170 R. A first end of the propshaft  154  can be coupled for rotation with the output pinion shaft  102  extending from the power take-off unit  26  while a second end of the propshaft  154  can be coupled for rotation with an input  174  of the rear drive module  162 . The input  174  can include input pinion shaft  178 . The rear drive module  162  can be configured to transfer rotational input from input  174  to the drive axleshafts  166 L,  166 R. The rear drive module  162  can include, for example a housing  182 , a secondary or second differential (not shown), a torque transfer device (“TTD”) (not shown) that is generally configured and arranged to selectively couple and transmit rotary power from the input  174  to the second differential, and a TTD actuator  186 . The second differential can be configured to drive the axleshafts  166 L,  166 R. The TTD can include any type of clutch or coupling device that can be employed to selectively transmit rotary power from the input  174  to the second differential, such as a multi-plate friction clutch for example. The TTD actuator  186  is provided to selectively engage and disengage the TTD, and can be controlled by control signals from the control system  34 . The TTD actuator  186  can be any power-operated device capable of shifting the TTD between its first and second modes as well as adaptively regulating the magnitude of the clutch engagement force exerted. 
     The control system  34  is schematically shown in  FIG. 1  to include a controller  190 , a group of first sensors  194 , and a group of second sensors  198 . The group of first sensors  194  can be arranged within the motor vehicle  10  to sense a vehicle parameter and responsively generate a first sensor signal. The vehicle parameter can be associated with any combination of the following: vehicle speed, yaw rate, steering angle, engine torque, wheel speeds, shaft speeds, lateral acceleration, longitudinal acceleration, throttle position, position of shift fork  150 , position of mode collar  142 , position of plunger  158 , and gear position without limitations thereto. The controller  190  can include a plunger displacement feedback loop that permits the controller  190  to accurately determine the position of the plunger  158  or of an element associated with the position of the plunger  158 . The group of second sensors  198  can be configured to sense a driver-initiated input to one or more on-board devices and/or systems within the vehicle  10  and responsively generate a second sensor signal. For example, the motor vehicle  10  may be equipped with a sensor associated with a mode selection device, such as a switch associated with a push button or a lever, that senses when the vehicle operator has selected between vehicle operation in a two-wheel drive (FWD) mode and an all-wheel drive (AWD) mode. Also, switched actuation of vehicular systems such as the windshield wipers, the defroster, and/or the heating system, for example, may be used by the controller  190  to assess whether the motor vehicle  10  should be shifted automatically between the FWD and AWD modes. 
     The vehicle  10  can normally be operated in the two-wheel drive (FWD) mode in which the power take-off unit  26  and the rear drive module  162  are both disengaged. Specifically, the mode collar  142  of the disconnect mechanism  90  is positioned by the disconnect actuator  94  in its first (2WD) mode position such that the input shaft  98  is uncoupled from the transfer shaft  110 . As such, substantially all power provided by the powertrain  14  is transmitted to the primary driveline  22 . Likewise, the TTD can disconnected such that the input  174 , the propshaft  154 , the output pinion shaft  102  and the transfer gear assembly  86  within the power take-off unit  26  are not back-driven due to rolling movement of the second vehicle wheels  170 L,  170 R. While the actuator  94  is described herein with reference to positioning the mode collar  142  to selectively change modes of the power take off unit  26 , the actuator  94  can be used on other clutched vehicle components such as other driveline components (not shown) or a suspension system (not shown), such as an electronically disconnecting sway bar for example. 
     When it is desired or necessary to operate the motor vehicle  10  in the all-wheel drive (AWD) mode, the control system  34  can be activated via a suitable input which, as noted, can include a driver requested input (via the mode select device) and/or an input generated by the controller  190  in response to signals from the first sensors  194  and/or the second sensors  198 . The controller  190  initially signals the TTD actuator  186  to engage the TTD to couple the input  174  to the axleshafts  166 L,  166 R. Specifically, the controller  190  controls operation of the TTD actuator  186  such that the TTD is coupled sufficiently to synchronize the speed of the secondary driveline  30  with the speed of the primary driveline  22 . Upon speed synchronization, the controller  190  signals the actuator  94  to cause the mode collar  142  in the power take-off unit  26  to move from its first mode position into its second mode position. With the mode collar  142  in its second mode position, rotary power is transmitted from the powertrain  14  to the primary driveline  22  and the secondary driveline  30 . It will be appreciated that subsequent control of the magnitude of the clutch engagement force generated by the TTD permits torque biasing for controlling the torque distribution ratio transmitted from the powertrain  14  to the primary driveline  22  and the secondary driveline  30 . 
     With additional reference to  FIGS. 3-5 , the disconnect actuator  94  can be a self-contained power-operated unit that can include the housing  156 , the plunger  158 , a first electromagnet  310 , a second electromagnet  312 , and a core assembly  314 . The housing  156  can include an outer case  316 , a first pole piece  318 , a second pole piece  320 , and a central pole piece  322 . The outer case  316  can be a generally cylindrical shape disposed about a central axis  324 . The outer case  316  can have a first end  326  and a second end  328 , and can define a central cavity  330  extending between the first and second ends  326 ,  328 . In the example provided, the outer case  316  is a round cylinder having an outer radial surface  332  and an inner radial surface  334 , though other configurations can be used. The inner radial surface  334  can define the central cavity  330 . In the example provided the outer case  316  is formed of a mild steel material, though other magnetic materials can be used. The first pole piece  318  can cap the first end  326  of the outer case  316  and the second pole piece  320  can cap the second end  328  of the outer case  316 . In the example provided, the first and second pole pieces  318 ,  320  are formed of a mild steel material, though other magnetic materials can be used. 
     The first pole piece  318  can be generally cylindrically shaped having a first outer radial surface  340 , a first inner side  342 , and a first outer side  344 , and can define a plunger aperture  346 . The plunger aperture  346  can penetrate axially through the first pole piece  318  from the first inner side  342  to the first outer side  344 . The plunger  158  can be slidably received through the plunger aperture  346 . The first pole piece  318  can be fixedly coupled to the outer case  316 . In the example provided, the first pole piece  318  is a cylindrical body received in the central cavity  330  at the first end  326  of the outer case  316 . The first outer radial surface  340  can abut and contact the inner radial surface  334  of the outer case  316 . While the first pole piece  318  is shown as a separate piece from the outer case  316 , the first pole piece  318  can alternatively be unitarily formed with the outer case  316 . The first inner side  342  can have a first docking surface  348 . In the example provided, the first docking surface  348  is an angled, or frustoconical surface formed coaxially about the axis  324  that converges toward the first outer side  344  and plunger aperture  346 . The first docking surface  348  can diverge and open into the central cavity  330  proximate to the first inner side  342 . 
     The second pole piece  320  can be generally cylindrically shaped having a second outer radial surface  360 , a second inner side  362 , and a second outer side  364 . The second pole piece  320  can also define a core aperture  366 . The core aperture  366  can penetrate through the second pole piece  320  from the second inner side  362  to the second outer side  364 , though other configurations can be used. The second pole piece  320  can be fixedly coupled to the outer case  316 . In the example provided, the second pole piece  320  is a cylindrical body received in the central cavity  330  at the second end  328  of the outer case  316 . The second outer radial surface  360  can abut and contact the inner radial surface  334  of the outer case  316 . While the second pole piece  320  is shown as a separate piece from the outer case  316 , the second pole piece  320  can alternatively be unitarily formed with the outer case  316 . The second inner side  362  can have a second docking surface  368 . In the example provided, the second docking surface  368  is an angled, or frustoconical surface formed coaxially about the axis  324  that converges toward the second outer side  364  and core aperture  366 . The second docking surface  368  can diverge and open into the central cavity  330  proximate to the second inner side  362 . 
     The central pole piece  322  can include a central body  380  and a bridge body  382 . The central pole piece  322  can be received in the central cavity  330  and spaced apart from the first and second pole pieces  318 ,  320 . The central body  380  can be generally ring shaped having a first side  384 , a second side  386 , and an outer radial surface  388  that can abut and contact the inner radial surface  334  of the outer case  316 . The central body  380  can extend radially inward from the inner radial surface  334  of the outer case  316  to an inner surface  390  distal to the inner radial surface  334 . The inner surface  390  can be parallel to the axis  324  and the inner radial surface  334 . The first side  384  can face toward the first end  326  of the outer case  316  and the second side  386  can face toward the second end  328  of the outer case  316 . The central body  380  can be formed of a mild steel, though other magnetic materials can be used. 
     The bridge body  382  can be generally ring shaped and can have a first base  410 , a second base  412 , and a span  414  extending between the first and second bases  410 ,  412 . The first base  410  can be axially between the first side  384  of the central body  380  and the first inner side  342  of the first pole piece  318 . The first base  410  can have a first base surface  416  and a third docking surface  418 . The first base surface  416  can face radially outward and be concentric with and radially spaced apart from the inner radial surface  334  of the outer case  316 . The third docking surface  418  can be an angled, or frustoconical surface formed coaxially about the axis  324  that converges toward the span  414  and the second end  328 . The third docking surface  418  can diverge and open toward the first end  326 . The second base  412  can be axially between the second side  386  of the central body  380  and the second inner side  362  of the second pole piece  320 . The second base  412  can have a second base surface  420  and a fourth docking surface  422 . The second base surface  420  can face radially outward and be concentric with and radially spaced apart from the inner radial surface  334  of the outer case  316 . The fourth docking surface  422  can be an angled, or frustoconical surface formed coaxially about the axis  324  that converges toward the span  414  and the first end  326 . The fourth docking surface  422  can diverge and open toward the second end  328 . The span  414  can be generally ring shaped and coaxial about the axis  324 . The span  414  can extend axially between the first base  410  and second base  412  and fixedly couple the first and second bases  410 ,  412 . In the example provided, the first base  410 , second base  412 , and span  414  are unitarily formed of a single piece of mild steel, though other configurations and magnetic materials can be used. The span  414  can have an outer span surface  424  and define a central span bore  426 . The outer span surface  424  can abut and contact the inner surface  390  of the central body  380 . The first base surface  416  and second base surface  420  can be radially outward of the outer span surface  424  such that the first and second bases  410 ,  412  can radially overlap a portion of the central body  380  to limit axial movement of the bridge body  382  relative to the central body  380 . 
     The first electromagnet  310  can be received within the central cavity  330  and disposed about the axis  324 . The first electromagnet  310  can include a first coil housing  440  and a plurality of first coils  442  disposed within the first coil housing  440  and wound about the axis  324  such that application of a first voltage across the first coils  442  can cause an electrical current to flow through the first coils  442  to produce a magnetic field (not shown) about the axis  324 . The first coils  442  can be configured to produce a magnetic field (not shown) having a first polarity when a positive voltage is applied across the first coils  442  (i.e. current flows through the first coils  442  in a first direction), and to produce a magnetic field (not shown) having a second, opposite polarity when a negative voltage is applied across the first coils  442  (i.e. current flows through the first coils  442  in an opposite direction). The first coil housing  440  can abut and contact the inner radial surface  334  of the outer case  316 , the first inner side  342  of the first pole piece  318 , the first side  384  of the central body  380 , and the first base surface  416  of the bridge body  382 . The first coil housing  440  can be formed of a non-magnetic material, such as brass or a plastic for example. The first base surface  416  can abut and contact an inner surface  444  of the first coil housing  440  to overlap with at least some of the first coils  442 . 
     The second electromagnet  312  can be received within the central cavity  330  and disposed about the axis  324 . The second electromagnet  312  can be axially spaced apart from the first electromagnet  310  by the central body  380  of the central pole piece  322 . The second electromagnet  312  can include a second coil housing  460  and a plurality of second coils  462  disposed within the second coil housing  460  and wound about the axis  324  such that application of a first voltage across the second coils  462  can cause an electrical current to flow through the second coils  462  to produce a magnetic field (not shown) about the axis  324 . The second coils  462  can be configured to produce a magnetic field (not shown) having a third polarity when a positive voltage is applied across the second coils  462  (i.e. current flows through the second coils  462  in the first direction), and to produce a magnetic field (not shown) having a fourth, opposite polarity when a negative voltage is applied across the second coils  462  (i.e. current flows through the second coils  462  in an opposite direction). The second coil housing  460  can abut and contact the inner radial surface  334  of the outer case  316 , the second inner side  362  of the second pole piece  320 , the second side  386  of the central body  380 , and the second base surface  420  of the bridge body  382 . The second coil housing  460  can be formed of a non-magnetic material, such as brass, or a plastic for example. The second base surface  420  can abut and contact an inner surface  464  of the second coil housing  460  to overlap with at least some of the second coils  462 . 
     The first and second coils  442 ,  462  can be configured such that the first and third polarities produce like poles proximate to the central body  380 . For example, when current flows through the first and second coils  462 , the positive (or north) poles of the first and second coils  442 ,  462  can be proximate to the central body  380  while the negative (or south) poles can be proximate to the first and second pole pieces  318 ,  320  respectively. Likewise, the second and fourth polarities can produce opposite poles such that the negative (or south) poles of the first and second coils  442 ,  462  can be proximate to the central body  380  while the positive (or north) poles can be proximate to the first and second pole pieces  318 ,  320  respectively. 
     The core assembly  314  can be received in the central cavity  330  and can be axially translatable between a first actuator position ( FIGS. 3 and 4 ) and a second actuator position ( FIG. 5 ). In the example provided, the first actuator position corresponds to the first mode position and the second actuator position corresponds to the second mode position. The core assembly  314  can include a central rod  480 , a first core block  482 , a second core block  484 , and a permanent magnet  486 . The core assembly  314  can include a core end block  488 . The central rod  480 , first core block  482 , second core block  484 , and permanent magnet  486  can be fixedly coupled for common axial translation. The first core block  482  can be disposed about the axis  324 , can define a central bore  490 , and can have a first mating surface  492  and a third mating surface  494 . The first mating surface  492  can be generally frustoconical in shape such that the first mating surface  492  radially overlaps with the first docking surface  348 . The first mating surface  492  and first docking surface  348  can be formed at similar angles such that the first mating surface  492  is configured to oppose or matingly engage and contact the first docking surface  348 . In the example provided, the first mating surface  492  and first docking surface  248  are formed at an angle greater than 0° and less than 90°. The third mating surface  494  can be generally frustoconical in shape such that the third mating surface  494  radially overlaps with the third docking surface  418 . The third mating surface  494  and third docking surface  418  can be formed at similar angles such that the third mating surface  494  is configured to oppose or matingly engage and contact the third docking surface  418 . In the example provided, the third mating surface  494  and third docking surface  418  are formed at an angle greater than 0° and less than 90°. The first core block  482  can be formed of a mild steel, though other magnetic materials can be used. 
     The second core block  484  can be disposed about the axis  324 , can define a central bore  510 , and can have a second mating surface  512  and a fourth mating surface  514 . The second mating surface  512  can be generally frustoconical in shape such that the second mating surface  512  radially overlaps with the second docking surface  368 . The second mating surface  512  and second docking surface  368  can be formed at similar angles such that the second mating surface  512  is configured to oppose or matingly engage and contact the second docking surface  368 . In the example provided, the second mating surface  512  and second docking surface  368  are formed at an angle greater than 0° and less than 90°. The fourth mating surface  514  can be generally frustoconical in shape such that the fourth mating surface  514  radially overlaps with the fourth docking surface  422 . The fourth mating surface  514  and fourth docking surface  422  can be formed at similar angles such that the fourth mating surface  514  is configured to oppose or matingly engage and contact the fourth docking surface  422 . In the example provided, the fourth mating surface  514  and fourth docking surface  422  are formed at an angle greater than 0° and less than 90°. The second core block  484  can be formed of a mild steel, though other magnetic materials can be used. 
     The permanent magnet  486  can be a generally cylindrical shape formed of a permanently polarized material having a positive (or north) pole  520  and a negative (or south) pole  522  facing axially opposite ends  326 ,  328 . In the example provided, the north pole is proximate to the first end  326  and the south pole is proximate to the second end  328 , though other configurations can be used. The permanent magnet  486  can define a central bore  524  and be disposed about the axis  324  axially between the first and second core blocks  482 ,  484 . The permanent magnet  486  can abut and contact the first and second core blocks  482 ,  484  and be spaced apart and radially inward of the bridge body  382 . The permanent magnet can have a magnetic field (not shown) of a strength sufficient to hold the core assembly  314  in the first and second actuator positions when the first and second electromagnets  310 ,  312  are unenergized, as will be discussed below. 
     The core end block  488  can be a generally cylindrical shape defining a central bore  530 . The core end block  488  can be received in the central cavity  330  and can be axially slidingly received in the core aperture  366 . The central rod  480  can be received through the central bores  490 ,  510 ,  524 ,  530  of the first core block  482 , second core block  484 , the permanent magnet  486 , and core end block  488 . The central rod  480  can couple the first core block  482 , second core block  484 , the permanent magnet  486 , core end block  488 , and plunger  158  together for common axial translation along the axis  324 . In the example provided, the central rod  480  is a bolt having a head  532 , a body  534  and a plurality of threads  536 , though other configurations can be used. The central bore  530  of the core end block  488  can have a counter bore  538  in which the head is received, and the plunger  158  can have a plurality of mating threads  540  with which the plurality of threads  536  can engage, in order to retain the first core block  482 , second core block  484 , and permanent magnet  486  between the plunger  158  and the core end block  488  for common axial translation. 
     In operation, the core assembly  314  can be configured to axially translate the plunger  158  which can move the shift fork  150  to translate the shift collar  142  between the first and second mode positions when the core assembly  314  translates between the first and second actuator positions. With specific reference to  FIG. 3 , the core assembly  314  is shown in the first actuator position with the first and second electromagnets  310 ,  312  in an unenergized state, wherein current does not flow through the first and second coils  442 ,  462  to generate a magnetic field (not shown). In this configuration, the permanent magnet polarizes the first and second core blocks  482 ,  484  (positive polarity indicated by “N”, negative polarity indicated by “S”) and generates a magnetic flux  550  that can flow through the housing  156  as shown. Specifically, the magnetic flux  550  can flow from the north pole  520 , through the first core block  482 , to the first pole piece  318 , to the outer case  316 , to the central body  380 , to the second base  412 , through the second core block  484  and to the south pole  522  of the permanent magnet  486 . This magnetic flux  550  can hold the core assembly  314  in the first actuator position without the need for continuous power to be provided to the actuator  94 . 
     With specific reference to  FIG. 4 , the core assembly  314  is shown in the first actuator position with the first and second electromagnets  310 ,  312  in a first energized state, wherein current flows through the first and second coils  442 ,  462  in the first direction to generate a first magnetic field (not shown). In this configuration, the magnetic field generated by the first and second electromagnets  310 ,  312  can polarize the first and second pole pieces  318 ,  320  with the same polarity, and can polarize the central pole piece  322  with a polarity opposite the first and second pole pieces  318 ,  320  (positive polarity indicated by “N”, negative polarity indicated by “S”). In this configuration, since the first core block  482  is positively polarized by the permanent magnet  486 , and the first pole piece  318  is positively polarized by the first electromagnet  310 , the first pole piece  318  and the first core block  482  are repelled from one another to urge the core assembly  314  axially in the direction away from the first end  326  and toward the second actuator position. Likewise, since the central pole piece  322  is negatively polarized by the first and second electromagnets  310 ,  312  and the second core block  484  is negatively polarized by the permanent magnet  486 , the central pole piece  322  and the second core block  484  are repelled from one another to also urge the core assembly  314  axially in the direction away from the first end  326 . Since the central pole piece  322  is negatively polarized and the first core block  482  is positively polarized, the first core block  482  is attracted to the central pole piece  322  to urge the first core block  482  toward the central pole piece  322 . Likewise, since the second pole piece  320  is positively polarized and the second core block  484  is negatively polarized, the second core block  484  is attracted to the second pole piece  320  to urge the core assembly  314  toward the second end  328 . These attractive and repulsive magnetic forces can move the core assembly  314  to the second actuator position. 
     With specific reference to  FIG. 5 , the core assembly  314  is shown in the second actuator position with the first and second electromagnets  310 ,  312  in the unenergized state, wherein current does not flow through the first and second coils  442 ,  462  to generate a magnetic field (not shown). In this configuration, the permanent magnet polarizes the first and second core blocks  482 ,  484  (positive polarity indicated by “N”, negative polarity indicated by “S”) and generates a magnetic flux  560  that can flow through the housing  156  as shown. Specifically, the magnetic flux  560  can flow from the north pole  520 , through the first core block  482 , to the first base  410 , to the central body  380 , to the outer case  316 , to the second pole piece  320 , through the second core block  484  and to the south pole  522  of the permanent magnet  486 . This magnetic flux  560  can hold the core assembly  314  in the second actuator position without the need for continuous power to be provided to the actuator  94 . Thus, once the core assembly  314  is in the second actuator position, power to the actuator  94  can be shut off, while maintaining the actuator  94  in the second actuator position. It is appreciated that the actuator  94  can be configured such that power could be cut off before the core assembly  314  fully reaches the second actuator position. In such a configuration, power could be cut off when the core assembly  314  reaches a position such that the magnetic field produced by the permanent magnet is sufficient to attract the core assembly  314  the remaining distance toward the second actuator position. To move the core assembly  314  from the second actuator position to the first actuator position, the current in the first and second coils  462  can be reversed to negatively polarize first and second pole pieces  318 ,  320  and positively polarize the central pole piece  322  to reverse the process and move the core assembly  314  axially toward the first end  326 . 
     With reference to  FIGS. 6 and 7 , an actuator  94 ′ of a second construction is illustrated. The actuator  94 ′ is similar to actuator  94  and similar features are represented by primed reference numerals. Accordingly, the discussion of the similar features from actuator  94  and vehicle  10  is incorporated herein by reference and only differences will be discussed in detail. The bridge body  382 ′ of the actuator  94 ′ can differ from the bridge body  382  in that the span  414 ′ can be axially longer than the span  414  and axially longer than the central body  380 ′ is thick (i.e. the thickness between the first side  384 ′ and second side  386 ′ of the central body  380 ′). When the core assembly  314 ′ is in the first actuator position ( FIG. 6 ), the magnetic flux  550 ′ can cause the second core block  484 ′ to hold the second base  412 ′ against the second side  386 ′ of the central body  380 ′. In this construction, the longer span  414 ′ causes the first base  410 ′ to extend axially toward the first end  326 ′ more than the second base  412 ′ extends axially toward the second end  328 ′, but while still being spaced apart from the first core block  482 ′. When the first and second electromagnets  310 ′,  312 ′ are energized, the negatively polarized first base  410 ′ of the bridge body  382 ′ is closer to the positively charged first core block  482 ′. The increased proximity of the first base  410 ′ to the first core block  482 ′ can increase the attractive force therebetween when the first electromagnet  310 ′ is energized to cause the actuator  94 ′ to move from the first actuator position to the second actuator position ( FIG. 7 ) more quickly. 
     When the core assembly  314 ′ moves from the first actuator position to the second actuator position, the first core block  482 ′ pushes the bridge body  382 ′ in the axial direction toward the second end  328 ′ to cause the bridge body  382 ′ to slide axially relative to the central body  380 ′. The bridge body  382 ′ can slide axially relative to the central body  380 ′ until the first base  410 ′ contacts the first side  384 ′ of the central body  380 ′. The first base  410 ′ can contact the first side  384 ′ when the core assembly  314 ′ is in the second actuator position and the second mating surface  512 ′ of the second core block  484 ′ contacts the second docking surface  368 ′ of the second pole piece  320 ′. In the second actuator position, the longer span  414 ′ causes the second base  412 ′ to then extend axially toward the second end  328 ′ similarly to the first base  410 ′ when the core assembly  314 ′ is in the first actuator position. This proximity of the second base  412 ′ to the second core block  484 ′ operates similarly when reversing the current in the first and second electromagnets  310 ′,  312 ′ to move the core assembly  314 ′ from the second actuator position to the first actuator position. 
     Similarly, when the core assembly  314 ′ moves from the second actuator position to the first actuator position, the second core block  484 ′ pushes the bridge body  382 ′ in the axial direction toward the first end  326 ′ to cause the bridge body  382 ′ to slide axially relative to the central body  380 ′. The bridge body  382 ′ can slide axially relative to the central body  380 ′ until the second base  412 ′ contacts the second side  386 ′ of the central body  380 ′. The second base  412 ′ can contact the second side  386 ′ when the core assembly  314 ′ is in the first actuator position and the first mating surface  492 ′ of the first core block  482 ′ contacts the first docking surface  348 ′ of the first pole piece  318 ′. 
     With additional reference to  FIG. 8 , an actuator  94 ″ of a third construction is illustrated. The actuator  94 ″ can be constructed in a similar manner as the actuator  94  with similar features represented by double primed reference numerals. Accordingly, the discussion of the similar features from actuator  94  and vehicle  10  is incorporated herein by reference and only differences will be discussed in detail. The actuator  94 ″ can further include an outer housing  810 , an axial compliance mechanism  812 , a first sensor  814 , a first target  816 , a second sensor  818 , and a second target  820 . In this construction, the central rod  480 ″ is not fixedly coupled to the first and second core blocks  482 ″,  484 ″, or the permanent magnet  486 ″. In contrast, the central rod  480 ″ is separate from the core assembly  314 ″, which includes the permanent magnet  486 ″, and the first and second core blocks  482 ″,  484 ″. The central rod  480 ″ is coaxial with the core assembly  314 ″ and axially slidable relative to the core assembly  314 ″. 
     The outer housing  810  can include a first shell  822  and second shell  824 . The first shell  822  can cap the first outer side  344 ″ of the first pole piece  318 ″ and can be partially disposed about the outer case  316 ″, such that the first end  326 ″ is received within the first shell  822 . The first shell  822  can be coupled to the outer case  316  to inhibit axial separation therefrom. In the example provided, the first shell  822  includes at least one clip  826  that is received in an indention  828  formed in the outer radial surface  332 ″ of the outer case  316 ″ to couple the first shell  822  to the outer case  316 . The first shell  822  can include a nose portion  830  that extends axially away from the first pole piece  318 ″. The nose portion  830  can include a plurality of external threads  832  that can be configured to mount the actuator  94 ″ to the vehicle  10 , such as to the housing  74  of the PTU  26  ( FIG. 2 ). The nose portion  830  can be a generally tubular body, within which the central rod  480 ″ can extend. 
     The second shell  824  can cap the second outer side  364 ″ of the second pole piece  320 ″ and can be partially disposed about the outer case  316 ″, such that the second end  328 ″ is received within the second shell  824 . The second shell  824  can be coupled to the outer case  316  to inhibit axial separation therefrom. In the example provided, the second shell  824  includes at least one clip  834  that is received in an indention  836  formed in the outer radial surface  332 ″ of the outer case  316 ″ to couple the second shell  824  to the outer case  316 . 
     The axial compliance mechanism  812  can include a first shaft or sleeve  850 , a second shaft or sleeve  852 , a tube  854 , a spring  856 , a first annular plate  858 , and a second annular plate  860 . The first sleeve  850 , first and second annular plates  858 ,  860 , spring  856 , and tube  854  can be disposed coaxially about the central rod  480 ″ between the first core block  482 ″ and the shift fork  150 ″. The first sleeve  850  can be axially between the first core block  482 ″ and the second annular plate  860 , and can contact the first core block  482 ″ and the second annular plate  860 . The first sleeve  850  can be received through the plunger aperture  346 ″. A first bumper  862  can be disposed about the first sleeve  850 , axially between the first pole piece  318 ″ and the first core block  482 ″. In the example provided, the first bumper  862  is a resilient O-ring configured to be received within a bore  864  defined by the first pole piece  318 ″ and to dampen an impact of the first core block  482 ″ with the first pole piece  318 . 
     The tube  854  can be axially slidable within the nose portion  830  of the outer housing  810  and can define a spring chamber  870 . A first end  872  of the tube  854  can be fixedly coupled to the plunger  158 ″ for common axial translation. A second end  874  of the tube  854  that is proximate to the first pole piece  318 ″ can define a bore  876  that has a diameter that is less than the diameter of the spring chamber  870 . The first sleeve  850  can be slidably received through the bore  876 . 
     The first annular plate  858  can have an inner diameter greater than the central rod  480 ″ and an outer diameter less than the spring chamber  870 , such that the first annular plate  858  is received in the spring chamber  870  about the central rod  480 ″. The second annular plate  860  can have an inner diameter greater than the central rod  480 ″ and an outer diameter less than the spring chamber  870 , such that the can be received in the spring chamber  870  about the central rod  480 ″. The outer diameter of the second annular plate  860  can be greater than the bore  876  and the inner diameter of the second annular plate  860  can be less than the bore  876  and the first sleeve  850 . The second annular plate  860  can be axially between the first annular plate  858  and the first sleeve  850 . 
     The spring  856  can be a coil spring disposed concentrically about the central rod  480 ″ within the spring chamber  870 . The spring  856  can be disposed axially between the first and second annular plates  858 ,  860 . The spring  856  can have a diameter greater than the inner diameters and less than the outer diameters of the first and second annular plates  858 ,  860 . 
     Each end of the central rod  480 ″ can include an end cap  880 ,  882  that extends radially outward from the rest of the central rod  480 ″. The end cap  880  that is proximate to the plunger  158 ″, can have a diameter that is greater than the inner diameter of the first annular plate  858  and less than the spring chamber  870 . In this way, the end cap  880  and the second end  874  of the tube  854  can retain the spring  856  and first and second annular plates  858 ,  860  within the spring chamber  870 . 
     The second sleeve  852  can be disposed coaxially about the central rod  480 ″. The second sleeve  852  can be axially between and can contact the second core block  484 ″ and the other end cap  882 . The second sleeve  852  can be received through the core aperture  346 ″. The other end cap  882  can have a diameter that is greater than the diameter of the second sleeve  852 , such that the other end cap  882  can retain the second sleeve about the central rod  480 ″. A second bumper  890  can be disposed about the second sleeve  852 , generally axially between the second pole piece  320 ″ and the second core block  484 ″. In the example provided, the second bumper  890  is a resilient O-ring configured to be received within a bore  892  defined by the second pole piece  320 ″ and to dampen an impact of the second core block  484 ″ with the second pole piece  320 . 
     The first target  816  can be fixedly coupled to the tube  854  for common axial translation therewith. The first sensor  814  can be disposed within the nose portion  830  and configured to detect the axial position of the first target  816 . The first sensor  814  can be one of the sensors within the group of first sensors  198  ( FIG. 1 ). The first sensor  814  and first target  816  can be any suitable type of sensor and target, such as a magnet and a hall effect sensor for example. 
     The second target can be fixedly coupled to the second sleeve  852  for common axial translation therewith. The second sensor  818  can be disposed within the second shell  824  and configured to detect the axial position of the second target  820 . The second sensor  818  can be one of the sensors within the group of first sensors  198  ( FIG. 1 ). The second sensor  818  and second target  820  can be any suitable type of sensor and target, such as a magnet and a hall effect sensor for example. 
     In general, the axial compliance mechanism  812  can transmit linear motion of the permanent magnet  486 ″ to linear motion of the plunger  158 ″, while permitting relative movement between the plunger  158 ″ and the permanent magnet  486 ″ in both axial directions. For example, if the internal spline teeth  146  of the shift collar  142  are blocked by the external clutch teeth  138  of the transfer shaft  110  ( FIG. 2 ), or are torque locked thereto, then the axial compliance mechanism  812  can permit the core assembly  314 ″ to still move axially between the first and second pole pieces  318 ″,  320 ″. The axial compliance mechanism  812  can then bias the plunger  158 ″ toward the first actuator position when the permanent magnet  486 ″ magnetically couples the first core block  482 ″ to the first pole piece  318 ″, and can bias the plunger  158 ″ toward the second actuator position when the permanent magnet  486 ″ magnetically couples the second core block  484 ″ to the second pole piece  320 ″. 
     In operation, when the first and second electromagnets  310 ″,  312 ″ are energized to repel the core assembly  314 ″ from the second pole piece  320 ″ and attract the core assembly  314 ″ toward the first pole piece  318 ″, the core assembly  314 ″ moves axially in a first direction  910 . The first core block  482 ″ pushes the first sleeve  850  axially in the first direction  910 . The first sleeve  850  pushes the second annular plate  860  axially in the first direction  910 . When the internal spline teeth  146  of the shift collar  142  are blocked by the external clutch teeth  138  of the transfer shaft  110  ( FIG. 2 ), the plunger  154 ″ is prevented from moving in the first direction  910 . Thus, the second annular plate  860  compresses the spring  856  within the tube  854  to bias the central rod  480 ″ and the plunger  158 ″ in the first direction  910 . The force of the spring  856  can be insufficient to overcome the magnetic coupling of the first core block  482 ″ to the first pole piece  318 ″, such that power does not need to be maintained to the first and second electromagnets  310 ″,  312 ″. When the shift collar  142  is no longer blocked, the spring  856  can then move the plunger  158 ″ in the first direction  910 . 
     When the first and second electromagnets  310 ″,  312 ″ are energized to repel the core assembly  314 ″ from the first pole piece  318 ″ and attract the core assembly  314 ″ toward the second pole piece  320 ″, the core assembly  314 ″ moves axially in a second direction  912 . The second core block  484 ″ pushes the second sleeve  852  axially in the second direction  912 . The second sleeve  852  engages the other end cap  882  to push the central rod  480 ″ axially in the second direction  912 . When the shift collar  142  and the transfer shaft  110  ( FIG. 2 ) are torque locked, the plunger  154 ″ is prevented from moving in the second direction  912 . Thus, the end cap  880  causes the first annular plate  858  to compress the spring  856  within the tube  854  to bias the plunger  158 ″ in the second direction  912 . The force of the spring  856  can be insufficient to overcome the magnetic coupling of the second core block  484 ″ to the second pole piece  320 ″, such that power does not need to be maintained to the first and second electromagnets  310 ″,  312 ″. When the shift collar  142  is no longer torque locked, the spring  856  can then move the plunger  158 ″ in the second direction  912 . 
     Since the first target  816  moves axially with the tube  854  and plunger  158 ″, the first sensor  814  can detect the position of the plunger  158 ″, and thus the position of the shift fork  150 ″. In this way, the first sensor  814  can detect if the shift collar  142  ( FIG. 2 ) is in the first mode position, the second mode position, or blocked in a position therebetween. 
     Since the second target  820  moves with the second sleeve  852 , which moves axially with the core assembly  314 ″, the second sensor  818  can detect the position of the core assembly  314 ″. In this way, the second sensor  818  can detect if the core assembly  314 ″ is in the first actuator position, the second actuator position, or some other position therebetween. The combination of the first and second sensors  814 ,  818  can allow for an independent determination of the condition or position of the actuator  94 ″ and shift collar  142 . 
     It is understood that the axial compliance mechanism  812  and/or the first and second sensors  814 ,  818  can also be incorporated into the actuators ( 94 ,  94 ′) of the first and second constructions, described above with reference to  FIGS. 3-7 . 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     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. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     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.