Patent Publication Number: US-2022230796-A1

Title: Solenoid with no metal-to-metal wear couples in default position

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 63/138,921, filed on Jan. 19, 2021, the entirety of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to solenoids, and more particularly relates to a solenoid actuator that includes no metal-to-metal wear couples in the default position of the solenoid. 
     BACKGROUND 
     Solenoid actuators are electromechanical devices that convert electrical energy into linear mechanical movement. Solenoid actuators are used in myriad environments and for many applications, and typically include at least a coil, a magnetically permeable shell or case, and a movable armature. When the coil is energized, a magnetic field is generated that exerts a force on the movable armature, moving it to a desired position. 
     One example end-use environment is the engine start system for an aircraft. A typical aircraft engine start system utilizes pressurized air, sourced via a ground cart, APU or adjacent engine, that is fed through a Start Air Valve (SAV) into an Air Turbine Starter (ATS) that is coupled to the aircraft main engine. A solenoid actuator is typically energized to control the position of the SAV, and is generally used only for initial engine starting or under failure conditions (in-flight engine shut down). As such, the system spends a majority of the aircraft duty cycle in a non-operative state. 
     For solenoid actuators in SAV applications, the default or de-energized condition is of particular interest due to its minimal operating time over aircraft life. A standard SAV solenoid actuator includes a combination of both metal-to-metal and non-metallic-on-metal wear couples to ensure acceptable internal wear in the default condition to facilitate reliable performance when energized for the required SAV service life. Recent commercial applications have pushed the limits of solenoid vibration capability. Designs that have offered robust performance in on legacy engines more often need improvement to meet life requirements in new engine applications. Design improvements include reducing metal to metal contact within the solenoid and upgrading to non-metallic components that exhibit more desirable wear properties. 
     Hence, there is a need for a solenoid actuator that includes no metal-to-metal contact at least when it is in the default position. The present invention addresses at least this need. 
     BRIEF SUMMARY 
     This summary is provided to describe select concepts in a simplified form that are further described in the Detailed Description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. 
     In one embodiment, a solenoid actuator includes a housing assembly, a bobbin assembly, a coil, an armature, an actuation rod, a guide ring, a lower spring guide, an upper spring guide, and a spring. The bobbin assembly is disposed at least partially within the housing assembly and includes a return pole and a yoke. The yoke has an inner surface that defines an armature cavity. The coil is disposed within the housing assembly and is wound around at least a portion of the bobbin assembly. The armature is disposed within the armature cavity and is axially movable relative to the yoke. The armature has an outer surface with a guide ring groove formed therein. The actuation rod is fixedly coupled to, and is axially moveable with, the armature. The guide ring is disposed within the guide ring groove and engages the inner surface of the yoke. The guide ring comprises a first non-metallic material. The lower spring guide is fixedly disposed within the return pole and has a lower spring guide opening through which the actuation rod extends. The lower spring guide comprises a second non-metallic material. The upper spring guide is spaced-apart from the lower spring guide and is disposed within the return pole. The upper spring guide is moveable with the actuation rod and comprises a third non-metallic material. The spring is disposed within the return pole and surrounds a portion of the actuation rod. The spring engages the upper spring guide and the lower spring guide. 
     In another embodiment, a solenoid actuator includes a housing assembly, a bobbin assembly, an interrupter, a coil, an armature, an actuation rod, a guide ring, a lower spring guide, an upper spring guide, a spring, and an anti-rotation structure. The bobbin is disposed at least partially within the housing assembly. The bobbin includes a return pole and a yoke that has an inner surface that defines an armature cavity. The interrupter is disposed between the return pole and the yoke. The coil is disposed within the housing assembly and is wound around at least a portion of the bobbin assembly. The armature is disposed within the armature cavity and is axially movable relative to the yoke. The armature has an outer surface with a guide ring groove formed therein. The actuation rod is fixedly coupled to, and is axially moveable with, the armature. The guide ring is disposed within the guide ring groove and engages the inner surface of the yoke. The guide ring comprises a first non-metallic material. The lower spring guide is fixedly disposed within the return pole and has a lower spring guide opening through which the actuation rod extends. The lower spring guide comprises a second non-metallic material. The upper spring guide is spaced-apart from the lower spring guide and is disposed within the return pole. The upper spring guide is moveable with the actuation rod and comprises a third non-metallic material. The spring is disposed within the return pole and surrounds a portion of the actuation rod. The spring engages the upper spring guide and the lower spring guide. The anti-rotation structure is disposed within the housing assembly and engages at least a portion of the armature. The anti-rotation structure comprises a fourth non-metallic material. The armature and the anti-rotation structure each have at least one feature formed thereon that mate with each other and thereby prevent rotation of the armature. The first, second, third, and fourth non-metallic materials each comprise materials selected from the group consisting of a thermoplastic polymer, a polytetrafluoroethylene (PTFE), and a fluorinated ethylene propylene (FEP) material. 
     Furthermore, other desirable features and characteristics of the solenoid actuator will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  depicts a cross section view of one example embodiment of a solenoid actuator; and 
         FIG. 2  depicts a cross section view of another example embodiment of a solenoid actuator. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. 
     Referring to  FIGS. 1 and 2 , cross section views of two exemplary embodiments of a solenoid actuator  100 ,  200  are depicted. The solenoid actuators  100 ,  200  each include at least a housing assembly  102 , a bobbin assembly  104 , a plurality of coils  106  ( 106 - 1 ,  106 - 2 ), and an armature  108 . The housing assembly  102  includes a housing  112  and a cover plate  114 . The housing  112  is configured to include a housing first end  116 , a housing second end  118 , and an inner surface  122  that defines a housing cavity  124 . The housing  112  may comprise any one of numerous materials having a relatively high magnetic permeability such as, for example, magnetic steel. The housing  112 , in addition to having a plurality of components disposed therein, provides a flux path, together with the bobbin assembly  104 , for magnetic flux that the coil  106  generates when it is electrically energized. The cover plate  114  is coupled to the housing first end  116 , and may also comprise any one of numerous materials having a relatively high magnetic permeability. 
     The bobbin assembly  104  includes at least a bobbin  126 , a return pole  128 , a yoke (or stop)  132 , and an interrupter  134 . The return pole  128  is fixedly coupled to the housing second end  118  and extends into the housing cavity  124 . The return pole  128  preferably comprises a material having a relatively high magnetic permeability. The return pole  128 , together with the housing  112 , the armature  108 , and the yoke  132  provides a magnetic flux path for the magnetic flux that is generated when the coils  106  are energized. The return pole  128  includes a return pole first end  136  and a return pole second end  138 . The return pole first end  136  extends into the housing cavity  124 . The return pole first end  136  is surrounded by, or at least partially surrounded by, the coils  106 , and defines an armature seating surface  142 . The return pole second end  138  defines a flange portion  144  that is disposed within the housing cavity  124 , and on which the bobbin  126  is disposed. 
     The interrupter  134  is disposed between the return pole  128  and the yoke  132  and is also disposed between the two coils  106 - 1 ,  106 - 2 . The interrupter  134  diverts the magnetic flux in the working air gap when the coils  106  are energized. The interrupter  134  may be manufactured from various non-magnetic materials, such as brass or non-magnetic steel (e.g. CRES  302 ). 
     The coils  106  are disposed within the housing  112  and are adapted to be electrically energized from a non-illustrated electrical power source. As noted above, when energized, the coils  106  generate magnetic flux. In the depicted embodiment, the coils  106  are wound around a portion of the bobbin  126 , and each comprises a relatively fine gauge (e.g.,  30 - 38  AWG) magnet wire, though larger gauge magnet wire could also be used. The magnet wire may be fabricated from any one of numerous conductive materials including, but not limited to, copper, aluminum, nickel, and silver. Although two coils  106  are depicted in  FIG. 1 , it will be appreciated that the solenoid actuator  100  could be configured with more or less than this number of coils, if needed or desired. 
     The armature  108  is disposed (at least partially) within the yoke  132 . More specifically, the yoke  132  has an inner surface  146  that defines an armature cavity. The armature  108  is disposed (at least partially) within the armature cavity and is axially movable relative to the yoke  132 . The depicted armature  108  includes an armature first end  148  and an armature second end  152 , and preferably comprises a material having a relatively high magnetic permeability. The armature first end  148  is at least partially surrounded by the coil  106  and defines a return pole engagement surface  154 . As noted previously, the armature  108 , together with the solenoid housing  112 , the return pole  128 , and the yoke  132 , provides a magnetic flux path for the magnetic flux that is generated by the coil  106  when it is energized. This results in axial movement of the armature  108  within the housing  112  between a first position and a second position. The armature  108  preferably comprises a metallic material, such as, for example, a magnetic iron. 
     The depicted solenoid actuator  100  additionally includes an actuation rod  156 , a pair of spring guides  158 —a lower spring guide  158 - 1  and an upper spring guide  158 - 2 —spring  162 , a guide ring  164 , and an anti-rotation structure  166 . The actuation rod  156  includes a first end  168  and a second end  172 . The actuation rod  156  is fixedly coupled, via its first end  168 , to the armature  108 , and extends through a return pole bore  174  that extends between the return pole first end  136  and the return pole second  138 . The actuation rod  156  also extends from the housing  102  to its second end  172 . The second end  172  is coupled to a component  150 , such as, for example, a valve, that is to be actuated by the solenoid actuator  100 . It will be appreciated that the actuation rod  156  may be fixedly coupled to the armature  108  using any one of numerous techniques. In the embodiment depicted in  FIG. 1 , it is fixedly coupled via mating threads that are formed on the armature  108  and the actuation rod  156 . In the embodiment depicted in  FIG. 2 , the actuation rod  156  is fixedly coupled to the armature  108  via braze joint. It should be noted that in both embodiments, this fixed coupling prevents any potential metal-to-metal sliding contact. 
     The spring guides  158  are disposed within the return pole bore  174  and surround different portions of the actuation rod  156 . More specifically, the lower spring guide  158 - 1  is fixedly disposed in the return pole bore  174  adjacent to the return pole second end  138  and includes a lower spring guide opening  176  and a lower spring guide land  178 . The actuation rod  156  extends through the lower spring guide opening  176 , which is dimensioned such that the actuation rod  156  is moveable relative to the lower spring guide  158 - 1 . The upper spring guide  158 - 2  is fixedly coupled to the actuation rod  156  and is moveable therewith within the return pole bore  174 . The upper spring guide  158 - 2  includes an upper spring guide opening  182  and an upper spring guide land  184 . The actuation rod  156  extends through the upper spring guide opening  182 , which is dimensioned such that the upper spring guide  158 - 2  is slip fit onto the actuation rod  156  and is retained against a larger diameter portion of the actuation rod  156 . The spring guides  158  are both formed of a non-metallic material, thereby eliminating metal-to-metal sliding contact between these spring guides  158  and the return pole  128 , and to improve wear resistance between the actuating rod  156  and spring guides  158  as well as the spring guides  158  and the return spring  162 . Some non-limiting examples of suitable non-metallic materials include, but are not limited to, a thermoplastic polymer, a polytetrafluoroethylene (PTFE), and a fluorinated ethylene propylene (FEP) material, just to name a few. 
     The spring  162  is disposed within the housing  102  and is configured to supply a bias force to the armature  108  that urges the armature  108  toward the first position. More specifically, the spring  162  is disposed within the return pole bore  174  and engages the lower spring guide  158 - 1  and the upper spring guide  158 - 2  via the lower and upper spring guide lands  178 ,  184 . Thus, the spring  162  supplies the bias force to the armature  108  via the upper spring guide  158 - 2  and the actuation rod  156 . The spring  162  may be formed of various metallic materials. In the depicted embodiment it is formed of 17-7 pH stainless steel. In other embodiments, however, it could be formed of other metallic materials, such as 300 Series CRES, just to name a few. 
     The guide ring  164  is coupled to and surrounds a portion of the armature  108 . The guide ring  164  is thus disposed within the armature cavity and is axially moveable, with the armature  108 , relative to the yoke  132 . The guide ring  164  is disposed within a guide ring groove  186  that is formed in an outer surface of the armature  108 . The guide ring  164  engages the inner surface  146  of the yoke  132  and is formed of a non-metallic material, thereby eliminating metal-to-metal sliding contact between the armature  108  and the yoke  132 . Some non-limiting examples of suitable non-metallic materials include, but are not limited to, a thermoplastic polymer, a polytetrafluoroethylene (PTFE), and a fluorinated ethylene propylene (FEP) material, just to name a few. 
     The anti-rotation structure  166  is disposed within the housing  102  and engages at least a portion of the armature  108 . The anti-rotation structure  166  and the armature  108  each have at least one feature formed thereon that mate with each other and thereby prevent any armature rotation that may occur when the coil  106  is de-energized, and/or if the solenoid actuator  100  is exposed to vibration. It will be appreciated that the anti-rotation structure  166  and the armature  108  may be variously configured to implement this function. Two different example configurations are depicted in  FIGS. 1 and 2 . Regardless of the particular configuration, the anti-rotation structure  166  is formed of a non-metallic material, thereby eliminating metal-to-metal sliding contact between the anti-rotation structure and the armature  108 . Some non-limiting examples of suitable non-metallic materials include, but are not limited to, a thermoplastic polymer, a polytetrafluoroethylene (PTFE), and a fluorinated ethylene propylene (FEP) material, just to name a few. 
     The solenoid actuator  100  disclosed herein includes various components that comprise a non-metallic material, such as a thermoplastic polymer, a polytetrafluoroethylene (PTFE), or a fluorinated ethylene propylene (FEP), and thus eliminate on metal-to-metal sliding contact. 
     In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical. 
     Furthermore, depending on the context, words such as “connect” or “coupled to” used in describing a relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically, electronically, logically, or in any other manner, through one or more additional elements. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.