Abstract:
Drive devices for coupling a drive mechanism to an input shaft and methods of providing coupling control through an electromagnet are described herein. The drive devices include a driven member operatively coupled to a clutch assembly engageable with an input shaft. The clutch assembly includes an electromagnet, an actuator activated by the electromagnet, and a clutch pack that is biased into increased frictional engagement by the actuator to transfer the torque from the driven member to the input shaft. The methods include providing such a drive device and activating the electromagnet.

Description:
RELATED REFERENCES 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/636,636, filed Apr. 21, 2012. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application relates generally to a clutch for linking a compressor with a drive means, in particular, an electromagnet and clutch pack assembly. 
       BACKGROUND 
       [0003]    Some automotive vehicles include an air compressor drive system such as those related to air-actuated braking systems. In such systems, compressed air is usually fed to a reservoir and, as needed, the reservoir supplies air to the braking system for brake actuation. The air compressor is typically activated or driven by the internal combustion engine via a transmission, usually with gears, which maintains operating pressure in the pneumatic system or systems. However, when there is no consumption of air, for example for braking, usually an automatic valve discharges any excess pressure in the system. To avoid inefficiencies, and the need to discharge air (when the air compressor output exceeds the brake system and reservoir requirements), the compressor may include a clutch that disengages the compressor when the pressure in the pneumatic system is equal to the maximum desired value and, reconnecting it as soon as its activation becomes necessary to restore working pressure. 
         [0004]    Current air compressors and the clutches therein provide for engagement and disengagement of the drive means and the compressor, but improvements are needed that out perform, last longer, and are more cost effective to manufacture. 
       SUMMARY 
       [0005]    In a first aspect, drive devices for coupling a drive mechanism to an input shaft are disclosed. The drive devices include a driven member operatively coupled to a clutch assembly engageable with an input shaft. The clutch assembly includes an electromagnet, an actuator activated by the electromagnet, and a clutch pack that is biased into increased frictional engagement by the actuator to transfer the torque from the driven member to the input shaft. The methods include providing such a drive device and activating the electromagnet. 
         [0006]    The actuator, in one embodiment, includes a rotor coupled to the driven member for rotation therewith, an armature rotatably coupled to a first plate, and a second plate rotatably coupled to the input shaft. The armature is axially translatable in response to activation and deactivation of the electromagnet. Activation moves the armature into a coupled relationship with the rotor for rotation therewith. The second plate is axially translatable relative to the first plate as the first plate rotates. During activation, the armature is rotatable with the rotor which results in the axial translation of the second plate, which moves members of the clutch pack into increased frictional engagement to transfer the torque from the driven member to the input shaft. 
         [0007]    In another aspect, air compressor drive devices with improved clutch assemblies are disclosed that utilize torque-sensitive coupling and de-coupling to permit one-way relative motion between a driven gear (driven by the crankshaft of an internal combustion engine) and an input shaft of an air compressor. When the driven gear is driven in the predominant direction of rotation and an electromagnet is activated, the clutching mechanism of the drive device is engaged and transfers the rotation of the driven gear to the input shaft of the air compressor. When the electromagnet is de-activated, the internal clutching mechanism disengages and the input shaft from the driven gear, thereby permitting the driven gear to continue to rotate independently of the input shaft of the air compressor. 
         [0008]    Accordingly, in another aspect, methods of providing coupling control through an electromagnet are disclosed. The methods include providing a drive device as disclosed herein and activating the electromagnet to activate the actuator such that the torque from the drive mechanism is transferred to the input shaft. Subsequently, the method may also include deactivating the electromagnet to uncouple the input shaft from the drive mechanism. 
         [0009]    One objection of the air compressor drive device is to provide improved efficiency of the vehicle air compressor system (or other systems) by providing coupling control through an electromagnet. 
         [0010]    Another object of the air compressor drive device is to provide a “soft” engagement of the clutch assembly, which reduces or eliminates vehicle disturbance at the point of compressor drive engagement/disengagement. 
         [0011]    In one embodiment, the drive devices for coupling a drive mechanism to an input shaft and methods of providing coupling control through an electromagnet are described herein. The drive devices include a driven member operatively coupled to a clutch assembly engageable with an input shaft. The clutch assembly includes an electromagnet, an actuator activated by the electromagnet, and a clutch pack that is biased into increased frictional engagement by the actuator to transfer the torque from the driven member to the input shaft. The methods include providing such a drive device and activating the electromagnet. 
         [0012]    Other advantages and features of the invention will be apparent from the following description of particular embodiments and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a perspective view of an assembled embodiment of an air compressor drive device. 
           [0014]      FIG. 2  is a cross-section view of the air compressor drive device of  FIG. 1 . 
           [0015]      FIG. 3  is an exploded, perspective view of the air compressor drive device of  FIG. 1 . 
           [0016]      FIG. 4  is an exploded, perspective view of a second embodiment of a ramp-ramp assembly suitable for use in the air compressor drive device illustrated in  FIG. 1 . 
           [0017]      FIG. 5  is an exploded, perspective view of a third embodiment of a ramp-ramp assembly suitable for use in the air compressor drive device illustrated in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description will illustrate the general principles of the invention, examples of which are additionally illustrated in the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. 
         [0019]      FIG. 1  is an illustration of a drive device, generally designated by reference numeral  100 , for use with a drive mechanism (not shown), such as an internal combustion engine of a vehicle, to couple the drive mechanism to an input shaft or other such load input of a system such as an air compressor included as part of a vehicle&#39;s air brake system. The drive device  100  includes a housing  101  that houses a clutch assembly  120  ( FIGS. 2 and 3 ) and has a driven gear  107  mounted to the exterior of the housing  101  by a fastener  114 . The housing  101  includes an outer jacket  126  and an inner casing  128  wherein the inner casing  128  nests within the outer jacket  128  as shown in  FIG. 2 . Within the vehicle, the housing  101  is fixedly mounted and the driven gear  107  is rotatable relative to the housing  101 . The driven gear  107  may be coupled directly or indirectly to other gears (not shown), which are ultimately coupled to the crankshaft of the drive mechanism. 
         [0020]    The fastener  114  may be a machine screw, bolt, or the like. In one embodiment, the machine screw has a keyed and tapered shaft that provides a connection, illustrated in  FIG. 2 , between the housing  101  and the input shaft of an air compressor  124 . A washer  111  and snap ring  112  may be used with the fastener  114 . 
         [0021]    Referring to  FIGS. 2 and 3 , the clutch assembly  120  includes an electromagnet or coil  102 , a clutch pack  106  of alternatively placed internally-splined plates  130  and externally-splined plates  132  ( FIG. 3 ), a rotor  115 , an armature  104 , a first ramp plate  103  and a second ramp plate  105  having their respective ramp features  160  and  162  in an opposite-profiled mating relationship, and roller bearings  109 ,  110 . The rotor  115  includes a central shaft  140  extending from a tub-shaped receptacle  142  configured to receive the electromagnet  102 . Central shaft  140  even extends beyond the upper edge  146  of the tub-shaped receptacle  142 . 
         [0022]    As illustrated in  FIG. 3 , the internally-splined plates  130  and externally-splined plates  132  are rings having central openings that are large enough to be seated around (i.e., circumferentially surround) the tub-shaped receptacle  142  portion of the rotor  115 . The exterior surface of the tub-shaped receptacle  142  includes a plurality of keyways  148  to receive the splines, individually, of the internally-splined plates  130 , and the interior surface of the inner casing  128  includes a plurality of keyways  129  to receive the splines, individually, of the externally splined plates  132 . Accordingly, the internally-splined plates  130  are rotatably connected to the rotor  115  for rotation therewith, and the externally-splined plates  132  are rotatably connected to the inner casing  128  for rotation therewith. This assembly provides a clutch pack  106  of interleaved plates  130  and  132  that are alternatively attached to input and output components. The internally-splined plates  130  and externally-splined plates  132 , input and output respectively, are free to rotate relative to each other when the electromagnet  102  is de-energized, providing no compressor drive and, conversely, when the clutch is activated (the electromagnet is energized) are compressed together (acted upon axially by the second ramp plate) into frictional engagement and rotate together which connects the input and output components for rotation together. 
         [0023]    The electromagnet  102  is attached to the outer jacket  126  and electrical power is supplied to the electromagnet  102  via wiring exiting through the outer jacket  126  (not shown). An energized coil or electromagnet  102  creates an electromagnetic field in the rotor  115  which attracts the armature  104  thereto and into contact with the bottom of its tub-shaped receptacle  142 . The armature  104  includes a splined or keyed flange  150  extending out from a first surface  152 . The first surface  152  is opposite the second surface  154 , which is the surface attracted to and placed into contact with the bottom of the rotor  115  when the electromagnet  102  is energized. 
         [0024]    Once the electromagnet  102  is energized and the armature  104  is attracted to the rotor  115 , the armature  104  rotates with the rotor  115 . The armature  104  through its splined flange  150  is keyed to the first ramp plate  103  for rotation together and, hence, rotation with the rotor  115  (in the energized state just described). This imparts a torque (from the driven gear  107 ) to the first ramp plate  103 . The first ramp plate  103  is most proximate the inner bottom surface  170  of the inner casing  128 , separated therefrom only by roller bearing  109 . Because the first ramp plate  103  includes a ramp feature  160  in an opposite-profiled mating relationship with a mating ramp feature  162  of the second ramp plate  105 , rotation of the first ramp plate  103  relative to the second ramp plate  105  causes the second ramp plate  105  to translate toward the rotor  115  as its mating ramp feature  162  slides along the ramp feature(s)  160  of the first ramp plate  103 . Accordingly, the torque of the first ramp plate  103  (provided by driven gear  107 ) is converted to axial force affiliated with the translation of the second ramp plate  105 . 
         [0025]    The second ramp plate  105  is splined similarly to the externally-splined plates  132 . The splines of the second ramp plate  105  are received in the keyways  129  of the inner casing  128  such that the second ramp plate is rotatable with the inner casing  128  and is also translatable (slidable along the axis of rotation) within the keyways  129 , hence the second ramp plate  105  is able to translate as discussed above. The second ramp plate  105  includes a rim  164  that defines a cavity  166  in which the armature  104  is seatable. The armature  104  is also axially translatable within the cavity  166  in response to the activation and deactivation of the electromagnet  102 . The rim  164  is configured to support the clutch pack  106 , and when the second ramp plate  105  translates toward the rotor  115 , an axial force is applied to the clutch pack  106  to clamp the alternating internally-splined plates  130  and externally-splined plates  132  together to enable torque transmission between the engine (via the driven gear  107 ) and the input shaft  122  ( FIG. 2 ) of the air compressor  124 . Once the second ramp plate  105  translates axially and clamps the clutch pack  106  the components of the clutch are engaged such that the rotatable components all rotate together in the predominant direction to rotate the input shaft  122 . 
         [0026]    When the air from the air compressor is no longer needed, the wiring connected to the electromagnet  102  is turned off and the electromagnet  102  is de-energized. As a result the armature  104  is no longer attracted to the rotor  115  and drops back to its seated positioned within the cavity  166 . The natural relative rotation rates of the rotor  115  (imparted thereto by the driven gear) and the deceleration of the inner casing  128  will rotate the second ramp plate  105  relative to the first ramp plate  103  thereby sliding the mating ramp features  162  of the second ramp plate  105  along the ramp features  160  of the first ramp plate in a direction opposite the predominant direction to axially translate the second ramp plate  105  away from the rotor  115  and thereby removing the axial force acting on the clutch pack  106 . The clutch is now unengaged. 
         [0027]    In the embodiment illustrated in  FIG. 3 , the ramp features  160  are gradually sloping wedges or inclined planes protruding from the upper surface of the first ramp plate  103 . As illustrated the wedges follow the curvature of the first ramp plate  103 . There may be two or more ramp features  160 . In one embodiment, three ramp features  160  may be preferred to provide stability to the plates. 
         [0028]    In another embodiment, as shown in  FIG. 4 , the ramp features of the first and second ramp plates  103 ,  105  may be a roller-ramp construction that expands axially (i.e., has at least one component that is translatable along the axis of rotation to a location that is further from another component thereof) as a result of rotational movement of one of the ramp plates. The first ramp plate  103  and the second ramp plate  105  in this embodiment have one or more roller elements  180  enclosed therebetween. The roller elements  180  are seated within inclined features  182  recessed into the facing surfaces of the first and second ramp plates  103 ,  105 . Each inclined features  182  defines a channel within which a roller element  180  may roll between a first end  192  that is shallow relative to a second end  194  (i.e., the second end is recessed more deeply into the surface of the ramp plate). For smooth angular displacement of the second ramp plate  104  as it translates (and rotation of roller elements  180 ) the channels are preferably smoothly, gradually tapering from the first end  192  to the second end  194 . The inclined features  182  in the two ramp plates  103 ,  105  are opposite-profiled inclined features (the orientation of the first end  192  and second end  194  of the inclined features  182  is reversed relative to the orientation of the first and second end of the inclined feature of the second ramp plate  105 ). As described above, in one embodiment rotation of the first ramp plate  103  results in translation of the second ramp plate  105 . The roller elements  180  may be cylinders, balls, generally conical cylinders, or the like. 
         [0029]    In another embodiment, as shown in  FIG. 5 , the ramp features of the first and second ramp plates, now generally designated as  203  and  205 , may be a cam-hurdle construction. The first ramp plate  203  includes a track or groove  214  that includes hurdles  216  spaced apart within the track  214 . The hurdles  216  may have arcuate ends having sloped or inclined surfaces facing the cams  208  protruding from the second ramp plate  205  such that relative rotation between the first ramp plate  203  and the second ramp plate  205  produces axial displacement (translation) of the second ramp plate  205  toward the rotor  115  and the clutch pack  106  as described above, as a result of the contour of the cams  208  moving rotationally along the hurdles  216 . Cams  208  include an upper surface  220  that is contoured to provide a camming action that results in the axial displacement of the second ramp plate  205  during rotation on at least one of the first and second ramp plates  203 ,  205 . The contour may include alternating, or even undulating, valleys  222  and peaks  224 . The valleys  222  of the contour are located opposite the hurdles  216  when the pulley assembly is in a rest position. Positive input from driven gear  107  through the rotor  115  ( FIGS. 2 and 3 ) results in relative rotation in a positive sense of the first ramp plate  203  when the electromagnet  102  is energized. In practice the ramp slopes, profiles on the hurdles  216 , and the contour of the upper surface  220  of the second ramp plate  205  may be different slopes or profiles. 
         [0030]    One benefit of these ramp-ramp, roller-ramp, or cam-hurdle constructions to actuate the clutch assembly, in particular to compress the clutch pack, is that each provides the drive device  100  with isolation or damping capability. 
         [0031]    As seen in  FIG. 2 , roller bearing  110  is disposed between the outer jacket  126  and the central shaft  140  of the rotor  115  to permit stable rotation of the rotor  115  relative to the outer jacket  126 . The use of a roller bearing may improve the overall structural rigidity of the assembly and extend the life of the assembly by reducing wear as elements of the clutching mechanism rotate relative to one another. 
         [0032]    In another embodiment, the clutch assembly  120  of  FIG. 3  or any of the other embodiments may include a spring (not shown) to bias the armature  104  to return to its seated position within the second ramp plate  105 . The spring may be a Belleville disc spring or wave spring, a coil spring, leaf spring, or the like. The spring may provide the benefit of controlled axial compliance, which if properly implemented, creates torsional isolation between the input and the output. 
         [0033]    As described above, the clutch system is ‘normally open’, no electrical power (an unenergized electromagnet) provides no compressor drive. Alternatively, the clutch system may be a ‘normally closed’ system (not shown), no electrical power (an unenergized electromagnet) provides a compressor drive. The clutch pack  106  and ramp plates  103 ,  105  (or  203 ,  205 ) provide soft engagement of the clutch and therefore the compressor, which can be modulated by varying the number of plates in the clutch pack and/or their compositions (e.g., selecting various materials for the plates and/or varying coefficients of friction). 
         [0034]    While splined connections are described and illustrated in the figures, the drive device  100  is not limited thereto. The drive device may include other coupling features configured to engage a mating coupling feature on another component of the clutch assembly  120  as long as such coupling features provide for rotation of one clutch component with another clutch component (i.e., transfer torque from one component to other component). 
         [0035]    Various parameters can affect the operation, responsiveness, and performance of the drive devices disclosed herein, including the angle, slope, or profile ramp or camming surfaces, and the coefficient of friction between components in frictional engagement with one another. Other factors that affect the selection of a particular combination include wear, primary clutching, durability and cost. 
         [0036]    In one aspect, the invention includes a drive device, for example to drive an air compressor, having a driven gear for coupling the drive device to an internal combustion engine, such as to its crankshaft, and an electromagnetic clutch. The clutch assembly includes an electromagnet seated within a rotor coupled to a driven gear for rotation therewith, an armature rotatably coupled to a first plate, the armature being translatable in response to the rotation of the first plate when it rotates with the armature, and a clutch pack comprising a plurality of plates that are compressible into frictional engagement with one another in response to the translation of the second plate to engage the clutch such that the clutch components rotate with the driven gear.