Abstract:
An electromagnetic transducer including a stator and an armature, the armature defining a first axis and being driven to ride between first and second couplers back and forth relative to the stator along the first axis. The second coupler is configured to permit movement of the armature along a second axis orthogonal to the first axis.

Description:
TECHNICAL FIELD  
       [0001]     This description relates to electromechanical transducing.  
       BACKGROUND  
       [0002]     The present invention relates in general to electromechanical transducing along a path and more particularly concerns an along-path, typically linear, controllable force source for actively absorbing energy from or applying energy to a vehicle wheel support assembly moving over a rough surface so as to facilitate significantly reducing forces transmitted to the vehicle body supported on the wheel support assembly.  
         [0003]     Electromechanical transducing may be used, for example, in vehicle suspensions. Vehicle suspensions employ a spring and shock absorber to isolate wheel motion from body motion. Some suspensions are variable and adaptive to driving conditions. For example, it is known to use electrically controlled active suspension members, such as an hydraulic piston actuator containing gas or fluid having a pressure that can be electrically controlled, to achieve a predetermined characteristic, such as a hard or soft ride, while avoiding bottoming.  
         [0004]     An electromagnetic transducer, such as a linear actuator, can be used in place of or in combination with the springs and/or shock absorbers and can include an armature mounted within a stator as described in U.S. Pat. No. 4,981,309 and incorporated here by reference. The armature can include bearing rails that slide within bearing trucks attached to the stator.  
       SUMMARY  
       [0005]     According to a first aspect, the invention features an apparatus including an electromagnetic transducer having a stator and an armature which defines a first axis. The armature is driven to ride between first and second couplers back and forth relative to the stator along the first axis. The second coupler is configured to permit movement of the armature along a second axis orthogonal to the first axis.  
         [0006]     In various embodiments, the apparatus includes an outer case having first and second portions. The armature can include first and second ends and configured to be slidably disposed within the case along the first axis.  
         [0007]     In one example, the first coupler is configured to couple the first end of the armature with the first portion of the case and the second coupler is configured to couple the second end of the armature with the second portion of the case. In another example, the second coupler is configured to impart high stiffness to the armature along a third axis orthogonal to both the first axis and the second axis.  
         [0008]     The first coupler can include a first linear bearing rail attached to a first end of the armature and a first bearing truck affixed to a first portion of the case. The first coupler can include a first linear bearing rail attached to a first portion of the case and a first bearing truck affixed to a first end of the armature.  
         [0009]     In various applications, the first bearing rail is slideably disposed in the first bearing truck. The first bearing truck can be aligned with the first end of the armature along a surface substantially parallel to the first axis. The second coupler can include a second linear bearing rail attached to the second end of the armature, and a second bearing truck disposed within the second portion of the case. In one application, the second bearing truck slideably engages the second portion of the case along the second axis.  
         [0010]     In one example, the apparatus includes set screws which extend from one or more of the bearing trucks and ride within slots disposed along the case to guide the movement of the armature. In another example, the second bearing truck slideably engages a recess disposed in the second portion of the case along the second axis for movement of the second end of the armature along the second axis.  
         [0011]     The second coupler can also include roller bearings positioned between the bearing surface and the bearing pockets for slideable engagement of the second end of the armature within the second portion of the case along the second axis. In one application, the second coupler includes roller bearings positioned between the bearing surface and the bearing pockets for rollable engagement of the second end of the armature within the second portion of the case along the first axis. In one example, the second end of the armature includes a bearing surface to engage a bearing pocket disposed within the second portion of the case.  
         [0012]     In one application, the apparatus includes roller bearings positioned between one or more of the ends of the armature and the case. The couplers can be low-friction blocks, such as delryn retainers for example, positioned between at least one of the ends of the armature and the case.  
         [0013]     In one example, the apparatus also includes a third coupler affixed to the second portion of the case. The third coupler can include a third bearing truck slideably coupled to the second bearing rail. The third coupler can also include a surface substantially parallel to the first axis to provide substantial alignment to the second coupler. In one application, the third coupler includes at least one recess disposed along the second portion of the case.  
         [0014]     In one application, the apparatus includes a first biasing element and a second biasing element extending from the second end of the armature to the second portion of the case. The first element can be configured to provide a first stiffness along a third axis orthogonal to the first axis and the second axis and the second element can be configured to provide a second stiffness along the second axis. In various examples, the first biasing element and the second biasing element can include a spring, a magnet, and/or an air bearing.  
         [0015]     According to another aspect, the invention features a vehicle having an active suspension system, a chassis and at least one wheel assembly. The wheel assembly includes at least one of the apparatus described in the first aspect to providing a controllable force between the wheel assembly and the chassis. The apparatus is configured such that the first coupler of the armature substantially faces the front of the vehicle and the second coupler substantially faces the rear of the vehicle.  
         [0016]     According to another aspect, the invention features a vehicle having an active suspension system, a chassis and at least one wheel assembly, and including at least one of the apparatus described in the first aspect for providing a controllable force between the wheel assembly and the chassis. The apparatus is configured such that the asymmetry in the load capacity of the couplers matches the asymmetry in the applied loads of the vehicle.  
         [0017]     According to another aspect, the invention features a vehicle having an active suspension system and including a chassis, at least one wheel assembly, and at least one of the apparatus described in the first aspect for providing a controllable force between the wheel assembly and the chassis. According to another aspect, the invention features a vehicle having an active suspension system and including a chassis, and at least two wheel assemblies, and each wheel assembly having at least one of the apparatus according to the first aspect for providing a controllable force between the wheel assembly and the chassis.  
         [0018]     According to another aspect, the invention features an electromechanical transducer including an outer case having a first portion and a second portion and housing a stator. The elongate armature extends along a first axis includes a first end and a second end and is configured to be slidably disposed within the case along the first axis. The transducer includes a first coupler to couple the first end of the armature with the first portion of the case and a second coupler to couple the second end of the armature with the second portion of the case. The second coupler is configured to allow controlled movement between the armature and the case along a second axis orthogonal to the first axis.  
         [0019]     According to another aspect, the invention features an electromechanical transducer including a case having a first portion and a second portion and an elongate armature which extends along a first axis. The armature is slidably disposed within the case along the first axis and along first and second bearing assemblies. The bearing assemblies are configured to include first and second linear bearing rails attached to first and second ends of the armature, respectively, and first and second bearing trucks attached to first and second portions of the case, the first and second bearing trucks configured to engage the first and second linear bearings, respectively. The second bearing assembly is configured to allow controlled movement between the second linear bearing rail and the second bearing truck along a second axis orthogonal to the first axis.  
         [0020]     According to another aspect, the invention features an active suspension system for a vehicle, where the system includes an electromechanical actuator. The actuator includes an outer case having a first portion and a second portion, an elongate armature extending along a first axis, having a first end and a second end and configured to be slidably disposed along the first axis, a first coupler to couple the first end of the armature with the first portion of the case and a second coupler to couple the second end of the armature with the second portion of the case. The second coupler is configured to allow controlled movement between the armature and the case along a second axis orthogonal to the first axis.  
         [0021]     According to another aspect, the invention features a method of controlling an electromechanical transducer including driving an elongate armature which defines a first axis between a pair of couplers back and forth along the first axis and configuring the armature and the couplers to permit movement of the armature along a second axis orthogonal to the first axis.  
         [0022]     According to another aspect, the invention features an apparatus having an electromagnetic transducer including a stator and an armature which defines a first axis. The armature is driven to ride between a pair of couplers back and forth relative to the stator along the first axis. Both the armature and the couplers are configured to provide a controlled amount of force in the armature along a second axis orthogonal to the first axis. In one application, the armature and the couplers are configured to provide a controlled amount of tension in the armature along the second axis. In another application, the armature and the couplers are configured to provide a controlled amount of compression in the armature along the second axis.  
         [0023]     According to another aspect, the invention features a method of controlling an electromechanical transducer including driving an elongate armature which defines a first axis between a pair of couplers back and forth along the first axis and configuring the armature and the couplers to provide a controlled amount of force in the armature along a second axis orthogonal to the first axis. In one application, the controlled amount of force provides a controlled amount of tension in the armature along the second axis. In another application, the controlled amount of force provides a controlled amount of compression in the armature along the second axis.  
         [0024]     Other advantages and features will become apparent from the description and from the claims. 
     
    
     DESCRIPTION  
       [0025]      FIG. 1  is a combined block-diagrammatic representation of a vehicle wheel suspension.  
         [0026]      FIG. 2  is a combined block-diagrammatic representation of an active wheel assembly.  
         [0027]      FIG. 3  is a perspective view of an electromechanical linear actuator.  
         [0028]      FIG. 4A  is a schematic top view of an electromechanical actuator.  FIG. 4B  is a detail view of a linear bearing depicted in the actuator of  FIG. 4A .  
         [0029]      FIGS. 5 and 6  are schematic top view of view of an electromechanical actuator.  
         [0030]      FIG. 7A  is a schematic top view of an electromechanical actuator.  FIG. 7B  is a detail view of a linear bearing depicted in the actuator of  FIG. 7A .  
         [0031]      FIG. 8A  is a schematic top view of an electromechanical actuator.  FIG. 8B  is a detail view of a linear bearing depicted in the actuator of  FIG. 8A .  
         [0032]      FIG. 9A  is a schematic top view of an electromechanical actuator housed within a two-part case.  FIG. 9B  is a detail view of a linear bearing depicted in the actuator of  FIG. 9A .  
         [0033]      FIG. 10  is a schematic side view of an electromechanical actuator.  
         [0034]      FIG. 11  is an overall view of active vehicle suspension system. 
     
    
       [0035]     Referring to  FIG. 1 , a suspension assembly  20  for a vehicle includes a wheel assembly  22  supporting the sprung mass  24  of the vehicle, typically about one-fourth the total mass of the vehicle, including the vehicle frame and components supported thereon (not shown). The sprung mass is connected to the wheel assembly by a spring-damper  25 , which includes a spring element  26  coaxial with a shock absorber  28 . Specifically, a wheel  30  includes a tire  32 , and a hub  34  which is mounted for rotation about an axle  36 . A wheel support assembly  38  connects the axle to the spring-damper assembly  25 . The wheel assembly and wheel support assembly are characterized by an unsprung mass Mw. A brake assembly (not shown) can also be a component of the unsprung mass. The tire is shown supported by a road surface  40 .  
         [0036]     Referring to  FIG. 2 , an exemplary active vehicle suspension assembly  50  includes an electromechanical actuator and a damping assembly. The sprung mass  24  is connected to a wheel support assembly  52  by an active suspension actuator  54  which is controlled by electronic controller  56 . A damping assembly including damping mass  58  connects to wheel support member with a damping spring  60  coaxial with clamping resistance element  62 , which can be a shock absorber, for example.  
         [0037]     Referring to  FIG. 3 , an example of an electromechanical actuator, a linear motor  70 , is configured for the active suspension assembly  50  ( FIG. 2 ). Such a suspension assembly is described in commonly owned U.S. Pat. No. 4,981,309, the contents of which are incorporated here by reference, as if fully set forth. The linear motor includes an inside member  72  which is slideably disposed within an outside member  74 . An exposed end of the inside member includes a bushing  76  pivotally connected to the unsprung mass (not shown), such as a wheel assembly as described above, for example. The outside member is pivotally connected at an end opposite the bushing to support member  78  attached to the sprung mass, such as the vehicle frame, for example. An outside member mounting frame  80  is affixed to an outside member pole assembly  82  and includes coils  88 . The inside member can include an array of rectangular magnets  84 . The outside member can include linear bearings  90  that slideably engage bearing rails  92   a ,  92   b  to facilitate relative movement between the inner and outer members.  
         [0038]      FIGS. 4A  to  9  provide schematic top views of an electromechanical actuator, such as the actuator depicted in  FIG. 3 , for example. Referring first to  FIG. 4A , a bearing system  110  allows an armature  112  to slide freely in the Z-direction as indicated, relative to an outer case  114 , along a linear bearing assembly  116   a  and  116   b . In one example, the armature  112  is elongate, and defines a longitudinal axis which extends generally in the Z-direction. At the same time, the bearing system can provide for constrained movement or high stiffness in the Y-direction to prevent the armature from impacting a stator, such as stacks  118   a  and  118   b , which can be coils  88  ( FIG. 3 ) as described above. The armature is attached to a pair of couplers. Couplers may comprise numerous types of bearing assemblies. In one embodiment, each coupler comprises a linear bearing rail and at least one bearing truck, where each coupler for example is attached at opposite ends of the armature. In other embodiments one or more couplers may comprise other bearing assembly types, such as roller bearings or magnetic bearings.  
         [0039]     The couplers permit the armature  112  to slide freely relative to the outer case  114  along a first direction (such as Z-direction as indicated), while limiting the relative movement of the armature  112  and the outer case  114  along a second direction (such as Y-direction as indicated). In one embodiment, the bearing rails are attached to the armature and the bearing trucks are attached to the stator. In another embodiment, bearing trucks are attached to the armature and bearing rails are attached to the stator. In some embodiments, couplers are fixedly attached to the stator (or the case housing the stator), such that motion of the armature in the X direction is constrained. In other embodiments, one of the couplers is attached to the stator or stator housing in a manner that allows some degree of relative motion between the coupler and the stator in the X direction to occur.  
         [0040]      FIG. 4B  shows the detailed view of how armature  112  engages the bearing truck  122   a , which applies to the discussion of all following relevant figures. Specifically, with reference to  FIG. 4B , the left side of the armature is attached to linear bearing rail  120   a  using screws  111 . The bearing rail  120   a  engages a bearing truck  122   a  which is rigidly attached to the case  114  using screws  121 . The armature slides freely in the Z-direction.  
         [0041]     Back to  FIG. 4A , on the right side of armature, a linear bearing rail  120   b  engages a bearing truck  122   b  and slides freely in the Z-direction. Bearing trucks  122   a ,  122   b  can be rigidly attached to case  114  and contain ball-bearing assemblies to allow for free relative motion in the Z-direction between the each rail and the corresponding truck.  
         [0042]     If the bearing trucks are both rigidly mounted to case as depicted in  FIG. 4A , then the mechanical assembly includes more constraints than required for dynamic equilibrium and is overconstrained in the X-direction. Unless the case and armature are machined with equally matched tolerances, the constraints will load the armature in either tension or compression along the X-direction. By careful design of the armature and case it is possible to purposely apply force to the armature  112 , thereby placing the armature in either tension or compression. Depending upon the application, such a design might be desirable. For example, placing armature in tension in the X-direction can increase the perceived stiffness of armature in the Y-direction, reducing the potential of the armature impacting the stacks  118   a ,  118   b . Placing armature into tension or compression also can increase the possibility of friction within the bearing trucks when the armature is sliding in the Z-direction. In order to eliminate this source of friction, the overconstraint in the X-direction can be reduced.  
         [0043]     Referring to  FIG. 5 , a bearing system  128  can address the overconstraint condition with modifications to the right-side bearing system, but it should be understood that similar modifications could be made to the left-side bearing system or both the right and left-side bearing systems. The armature  112  is allowed to slide freely in the Z-direction relative to the case  129 . A right-side bearing  130  can provide for free motion in the Z-direction, high stiffness in the Y-direction, and low stiffness in the X-direction. Biasing elements  132   a  and  132   b  are elements providing high stiffness in the Y-direction and biasing element  134  is an element providing low stiffness in the X-direction. In practice, it is possible to implement these biasing elements with a variety of devices including mechanical components, such as springs, magnetic components, and/or an air bearing system.  
         [0044]     Another example of a bearing system  135  is shown in  FIG. 6 , including a left-side bearing truck  136  shown rigidly attached to a case  138  using screws  140 . A right-side bearing truck  142  is shown “floating” relative to the case  138  using set-screws  144 . By appropriately designing the width of the case  138  and the width of the armature  112 , a predetermined gap  146  can be established between the case  138  and the bearing truck  142 . Designing bearing truck pockets  148   a ,  148   b  to be slightly oversized relative to bearing truck  142  establishes stiffness along the Y-direction. As the movement of the right-side bearing is constrained in the Y-direction but is permitted along the X-direction, this assembly provides for substantially high stiffness in the Y-direction and substantially no stiffness in the X-direction. As such, the overconstraint condition is addressed and the movement of the armature  112  in the Z-direction in substantially unrestricted.  
         [0045]     In another implementation, a bearing system  149  shown in  FIG. 7A , includes the left-side bearing truck  136  rigidly attached to a case  150  using screws  140 . The right-side bearing assembly includes a bearing surface  152  connected to the right side of the armature  112 . To prevent the armature  112  from contacting stacks  118   a  and  118   b , while moving in the Z-direction, roller bearings  154   a ,  154   b  may be used.  FIG. 7B  illustrates further details of the engagement of the armature  112  and the roller bearings  154   a ,  154   b  and the movement of the armature  112  along the Z-direction. To achieve high Y-direction stiffness, bearing pockets  156   a ,  156   b  are designed to be at least slightly larger than the thickness of armature  112  plus the thickness of the roller bearings  154   a ,  154   b . Referring back to  FIG. 7A , a gap  158  can be established between the side surface  151  of case  150  and the side surface  153  of the right-side bearing assembly which significantly reduces stiffness in the X-direction. As with the bearing assembly  135  of  FIG. 6 , this assembly provides for substantially high-stiffness in the Y-direction and substantially reduced or no stiffness in the X-direction. In one example, the left-side bearing assembly implemented by bearing truck  136  and bearing rail  120   a  provides enough stiffness in the Y-direction such that the right-side bearing assembly does not need to provide any additional stiffness for the armature. In this example, roller bearings  154   a ,  154   b  can be eliminated.  
         [0046]     In another example, a bearing system  159  shown in  FIG. 8A , includes the left-side bearing truck  136  rigidly attached to a first portion of the case  150  using screws  140 . A right end of the armature  112  is connected to a bearing rail  160  with a spring  162 . Bearing truck  164  is then rigidly attached to case  150  using screws  166 . By adjusting the stiffness of spring  162 , it is possible to adjust the level of friction that develops when armature  112  slides in the Z-direction. Spring  162  can represent the compliance of armature  112  and not be a physically separate element. Guides  170   a ,  170   b  can be used to provide additional stiffness in the Y-direction. In one example, as shown in  FIG. 8B , low-friction blocks  172   a ,  172   b  such as delryn retainers, for example, are rigidly attached to the guides  170   a  and  170   b  to provide substantially high-stiffness in the Y-direction and substantially no stiffness in the X-direction between guides  170  and armature  112 .  
         [0047]     In another example, a bearing system  174  shown in  FIG. 9A , includes the left-side bearing truck  136  rigidly attached to a left case-half  176  using screws  140 . Similarly, right-side bearing truck  178  is shown rigidly attached to a right case-half  177  using screws  180 . Compliance in the X-direction is provided by springs  182   a ,  182   b  extending between the left and right case-halves  176 ,  177 . Springs  182   a ,  182   b  can represent the compliance of the case-halves and not be physically separate components. Referring to  FIG. 9B , guides  184   a ,  184   b  and low friction blocks  186   a ,  186   b  such as delryn retainers, for example, can be provided for additional Y-direction stiffness.  
         [0048]     Without loss of generality, it should be understood that more than one bearing truck can be provided to engage the bearing rail extending along the Z-direction to provide additional stiffness in the Y-direction. Referring to  FIG. 10 , for example, a bearing system  188  includes a bearing rail  190  which slides in the Z-direction relative to case  192 . Bearing trucks  194  and  196  can represent either left-side or right-side bearings in the descriptions of  FIGS. 1 through 6 . As such, bearing trucks  194 ,  196  can be either fixed to the case  192  or floating relative to the case. In the bearing system  188 , bearing trucks  194 , and  196  can be aligned in the Z-direction. This is accomplished using reference surface  200  (which forms one side of the bearing pocket). Reference surface  200  could be machined in one operation so as to guarantee the alignment of the two trucks.  
         [0049]     Referring to  FIG. 11  and in one example, the actuators  210  form part of an integrated and active suspension control system for a vehicle  212 . Actuators  210  are integrated at each wheel of the front and rear suspension systems  214 ,  216 , respectively, of the vehicle as described with reference to  FIG. 2 . The actuators  210  can form part of the structural suspension linkage connecting the wheel assembly to the vehicle frame. The load capacity of the actuators  210  is asymmetric in that the load of the bearing is stronger in compression than in tension in a fore-aft direction. The dynamic loads applied to the bearings by the vehicle are asymmetric in that the applied loads are substantially greater during braking than acceleration. The actuators can be positioned within the vehicle to match the asymmetry in the load capacity of the bearing with the asymmetry in the applied loads of the vehicle. In one example, a first side of the actuator  220  including a fixed or rigidly attached bearing truck, such as the left-side bearing truck  136  ( FIG. 6 ) is positioned toward the front of the vehicle and a second side of the actuator  222  including a floating bearing truck, such as the right-side bearing truck  142  ( FIG. 6 ) is positioned toward the rear of the vehicle.  
         [0050]     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, although the described applications for the bearing systems include active vehicle suspensions, other applications that require an electrically controllable relative force between sprung and unsprung masses, are contemplated. Accordingly, other embodiments are within the scope of the following claims.