Abstract:
A method and apparatus for sensing magnetic field flux formed by current passing through a conductor, the apparatus comprising a rigid magnetically permeable core extending between facing first and second ends and formed about a conductor receiving space, the first and second ends forming first and second guide couplers, respectively, and defining a mounting gap therebetween having a mounting gap dimension, a resilient clip member including first and second clip couplers at oppositely facing first and second edges, respectively, the first and second guide couplers operably receiving the first and second clip couplers, respectively, to mount the clip within the mounting gap with a sensing space formed on a first side of the clip member between the first and second ends and a magnetic flux sensor mounted to the first side of the clip member substantially within the sensing space.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The field of the invention is Hall effect current sensors and more specifically methods and apparatus for mounting a magnetic field sensor within a gap formed by a core or flux guide that surrounds a conductor. 
     When current passes through a conductor, the current generates a magnetic field including flux that encircles the conductor and that is directed along flux lines in a direction consistent with the well known right hand rule. The field strength is strongest at locations in close proximity to the conductor. The magnitude of current passing through the conductor is directly proportional to the total strength of the magnetic field generated thereby. Thus, if the magnetic flux generated by the current can be accurately determined, then the magnitude of the current passing through that conductor can also be determined. 
     One way to determine the magnetic flux and hence conductor current has been to design a sensor configuration that relies upon the well known Hall effect electromagnetic principle. To this end, in 1879, Edwin Hall discovered that equal-potential lines in a current carrying conductor are skewed when put in the presence of a magnetic field. This effect was observed as a voltage (Hall voltage) perpendicular to the direction of current flow. Today, Hall effect devices for measuring the Hall voltage and hence a corresponding magnetic field are packaged as single Hall effect chips and are sold as high volume commodity items. 
     A typical current sensor utilizing Hall effect technology consists of a toroid or rectangular shaped gapped core and a Hall effect chip. Exemplary cores typically include either a laminated stack or a high resistivity solid ferrite material designed to prevent unwanted eddy currents. A single current carrying conductor is positioned within the core such that the permeable core directs the magnetic flux through the core and across the gap. A Hall effect chip is placed within the gap to sense the flux density passing there across. In a well-designed Hall effect current sensor, the measured flux density is linear and directly proportional to the current flowing through the current carrying conductor. 
     One design challenge routinely faced when designing Hall effect sensors has been finding a cost effective and mechanically robust way in which to mount the Hall effect chip within a core gap. One other challenge has been to configure a sensor that has a relatively small volume footprint. With respect to cost, as with most mechanical products, minimal piece count, less and simplified manufacturing steps and less manufacturing time are all advantageous. With respect to robustness, many Hall effect sensors are designed to be employed in rugged environments such as industrial control applications where shock and vibration are routine. 
     The industry has devised several Hall effect sensor configurations. For instance, in one configuration, a donut shaped and gapped ferrite core is positioned over a vertically mounted Hall effect chip which is soldered to a circuit board. In this case the ferrite core is typically manually positioned with respect to the chip and is then glued to the circuit board. While this solution can be used to provide a robust sensor configuration, this solution has several shortcomings. First, sensor manufacturing experience has revealed that it is relatively difficult to accurately position and glue a donut shaped core relative to the circuit board mounted Hall effect chip. Also, in this regard, where the sensor is subjected to vibrations and shock, any loosening or shifting of the bond between the core and board can compromise the accuracy of the current sensor. 
     Second, the manual labor to glue a core to a board is not very efficient or cost effective and the glue curing cycle is typically relatively long. Labor and curing costs increase the overall costs associated with providing these types of Hall effect current sensors. 
     One other approach to mounting a Hall effect chip within a core gap has been to mount the chip on a board, position the core in a housing cavity with the circuit board mounted chip appropriately juxtaposed within the gap, fill the cavity with epoxy potting compound and bake the filled housing for several hours to completely cure the epoxy. As in the case of the glued donut shaped core, the manual labor required to pot the core and board is relatively expensive. Moreover, the baking time required to cure the epoxy reduces manufacturing throughput. Furthermore, the requirement for a housing increases parts count and hence overall configuration costs. 
     Yet one other approach to mounting a Hall effect chip within a core gap has been to mount a circuit board within a bobbin and mount a Hall effect chip to the circuit board where right angle pin connectors from the chip protrude out of apertures in the bobbin for connection to one or more other circuit boards. A core lamination stack is inserted into the bobbin with the bobbin formed to arrange the core and chip with respect to each other such that the chip is within the gap. Thereafter, the bobbin, core, chip and board are inserted into a first piece of a housing with the pin connectors protruding out housing apertures and a second housing piece is snapped together with the first piece to secure all of the components inside. The housed configuration forms a complete Hall effect current sensor. 
     This solution, unfortunately, requires a relatively large number of components and therefore increases costs appreciably. In addition, the pin connectors used with this type of assembly are relatively flimsy and have been known to break when used in typical industrial environments. Moreover, the pin connectors are often bent prior to installation or may be located imperfectly and therefore make installation relatively difficult. Furthermore, if the laminations are not clamped tightly by the housing, the laminations may shift laterally or rotate within the housing due to shock or vibrations. Such shifting and rotation will often result in changing the size of the core gap which alters the sensitivity of the sensor configuration. 
     Thus, prior approaches for securing Hall effect chips within core gaps have each had one or more shortcomings and therefore it would be advantageous to have an apparatus and method for mounting chips within gaps that is simple, inexpensive and robust. 
     BRIEF SUMMARY OF THE INVENTION 
     It has been recognized that a robust and relatively inexpensive apparatus can be provided to secure a sensing chip within a flux guide or core gap which reduces the costs associated with manufacturing Hall effect type current sensors and that overcomes many of the shortcomings described above. To this end, generally, a small circuit board member referred to generally herein as a clip member, is configured to which a flux sensor is mounted. The edges of the clip member and the facing ends of the permeable core are configured such that they form couplers that cooperate to mechanically mount the clip and an attached sensor within the gap. More specifically, the clip edges are formed so as to be resiliently temporarily deformable so that the clip member can be forced into the gap between the guide ends. The clip edges also generally are formed with some type of restraining and/or retaining members that cooperate with structure formed by the guide ends to essentially eliminate relative movement between the clip and the core. 
     Thus, the present invention is an extremely inexpensive solution for mounting a magnetic field sensor within an air gap of a permeable core. In addition, the inventive solution is completely mechanical and therefore messy potting and epoxy steps are not necessary. Furthermore, the inventive solution is extremely quick to configure and hence manufacturing time required to employ the solution is minimized thereby further reducing solution costs. 
     Consistent with the above discussion, the present invention includes, among other things, sensor apparatus for sensing magnetic field flux formed by current passing through a conductor, the apparatus comprising a rigid flux guide core extending between facing first and second ends and formed about a conductor receiving space, the first and second ends forming first and second guide couplers, respectively, and defining a mounting gap there between having a mounting gap dimension, a resilient clip member including first and second clip couplers at oppositely facing first and second edges, respectively, the first and second guide couplers operably receiving the first and second clip couplers, respectively, to mount the clip within the mounting gap with a sensing space formed on a first side of the clip member between the first and second ends and a sensor mounted to the first side of the clip member substantially within the sensing space. 
     The invention also includes a method for use with a rigid guide core extending between facing first and second ends and formed about a conductor receiving space, the first and second ends forming first and second guide couplers, respectively, and defining a mounting gap therebetween having a mounting gap dimension, the method also for use with a sensor mounted to a resilient clip member including first and second clip couplers at oppositely facing first and second edges, respectively, the method for configuring a flux sensing assembly for sensing the flux generated by a current passing through a conductor, the method comprising the steps of positioning the conductor within the conductor receiving space and engaging the first guide and first clip couplers and the second guide and second clip couplers to secure the clip member between the first and second ends with the sensor substantially residing between the first and second ends. 
     In addition, the invention includes a method for configuring a sensor assembly for sensing the flux of a magnetic field formed by current passing through a conductor, the method comprising the steps of providing a rigid guide core extending between facing first and second ends and formed about a conductor receiving space, the first and second ends forming first and second guide couplers, respectively, and defining a mounting gap therebetween having a mounting gap dimension, providing a resilient clip member including first and second clip couplers at oppositely facing first and second edges, respectively, the first and second guide couplers configured to operably receive the first and second clip couplers, respectively, to mount the clip within the mounting gap with a sensing space formed on a first side of the clip member between the first and second ends, mounting a sensor to the first side of the clip member, positioning the conductor within the conductor receiving space and engaging the first guide and first clip couplers and the second guide and second clip couplers to secure the clip member between the first and second ends with the sensor substantially residing between the first and second ends. 
     Moreover, the invention includes a sensor mounting apparatus for use with a rigid guide core extending between facing first and second ends and formed about a conductor receiving space, the first and second ends forming first and second guide couplers, respectively, and defining a mounting gap therebetween having a mounting gap dimension, the apparatus for mounting a flux sensor within the gap, the apparatus comprising a resilient clip member including first and second clip couplers at oppositely facing first and second edges, respectively, the first and second clip couplers formed so as to be operably received by the first and second guide couplers, respectively, to mount the clip within the mounting gap with a sensing space formed on a first side of the clip member between the first and second ends, the first side formed to receive the sensor. 
    
    
     These and other objects, advantages and aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first Hall effect type current sensor embodiment; 
     FIG. 2 is a perspective view of the clip assembly illustrated in FIG. 1; 
     FIG. 3 is a top plan view of the clip assembly of FIG. 2; 
     FIG. 4 is a side plan view of the clip assembly illustrated in FIG. 2 ; 
     FIG. 5 is a side elevational view of the guide core of FIG. 1; 
     FIG. 6 is a partial view of one end of the core of FIG. 5 taken along the lines  6 — 6 ; 
     FIG. 7 is a perspective view similar to FIG. 1, albeit illustrating a second embodiment of a inventive Hall effective type sensor; 
     FIG. 8 is a perspective view of the clip assembly of FIG. 7; 
     FIG. 9 is a top plan view of the clip assembly of FIG. 8; 
     FIG. 10 is a side plan view of the clip assembly of FIG. 8; 
     FIG. 11 is a partial cross-sectional view taken along the line  11 — 11  of FIG. 7 illustrating only the facing ends of the core; and 
     FIG. 12 is a partial view of one end of the core of FIG. 11 taken along the line  12 — 12 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings and, more specifically referring to FIGS. 1 through 6, a first embodiment  10  of the present invention includes, generally, a permeable guide core  12  and a sensor assembly  60 . Core  12  includes a plurality of metallic laminations stacked together to form a substantially “C” shaped core having parallel members  16  and  20 , a substantially elongated and straight member  18  that traverses the distance between adjacent ends of parallel members  16  and  20  and relatively shorter members  14  and  22  that extend from ends of members  16  and  20  opposite member  18  and toward each other. Members  14  and  22  terminate at distal and facing first and second core ends  25  and  27 , respectively, that form a gap therebetween. Thus, members  14 ,  15 ,  16 ,  18 ,  20  and  22  together form a core around a space  26 . When mounted to a conductor, the conductor is positioned so as to pass through space  26 . Hereinafter, space  26  will be referred to as a conductor receiving space. Core  14  is characterized by a core thickness T g . (see FIG. 6) that corresponds to the combined thickness of the laminates used to construct core  12 . 
     Referring specifically to FIGS. 1 and 5, first and second passageways or recesses  28  and  30  are formed in the first and second ends  28  and  30 , respectively, such that the passageways  28  and  30  form substantially parallel and oppositely facing elongate internal surfaces  36  and  38 , respectively. Each of the internal surfaces  36  and  38  extends generally across the thickness T g  (see FIG. 6 again) of a corresponding end (e.g.,  25 ,  27 ). The facing internal surfaces  36  and  38  generally define a gap dimension D g . The space between ends  25  and  27  that is bounded on one side by the conductor receiving space  26  and bounded on the other side by passageways  28  and  30  will be referred to hereinafter as a sensor receiving space  29  while the space between ends  25  and  27  and on a side of passageways  28  and  30  opposite sensor receiving space  29  will be referred to hereinafter as a circuit receiving space  31 . As best illustrated in FIG. 5, ends  25  and  27  extend further toward each other proximate sensor receiving space  29  than they do proximate circuit receiving space  31 . Thus, looking into the gap formed by ends  25  and  27 , shelf surfaces  40  and  42  formed by ends  25  and  27  proximate space  29  are observable and a sensor receiving dimension D s  corresponding to sensor receiving space  29  is smaller than a circuit receiving space dimension D c  corresponding to circuit receiving space  31 . As illustrated, gap dimension D g  is greater than each of dimensions D c  and D s . The dimension between shelf surface  40  and space  26  (i.e., the vertical dimension of end  25  along space  29 ) must be large enough to accommodate flux sensor  94  when assembly  60  is mounted as illustrated in FIG.  1 . 
     Referring again to FIGS. 1 through 4, assembly  60  includes a clip member  51 , a plug receiving socket  96 , circuit components  100  and a flux sensor  94 . Clip member  51  is a substantially flat and relatively thin lightweight member which is typically formed of some type of circuit board material. Member  51  is generally rectangularly shaped and forms first and second oppositely facing edges  64  and  66  and third and fourth oppositely facing edges  76  and  78  and has first and second oppositely facing sides  92  and  98 , respectively. First side  92  of member  51  is formed in any manner well known in the art for mounting sensor  94  via soldering or some other mounting process. Similarly, second side  98  is constructed and designed to receive various circuit components  100  and also to receive plug socket  96  which, as its label implies, is configured to receive a plug for linking sensor  94  and other circuit components  100  to other circuitry. Sensor  94  and components  100  are operably linked via circuit board runs to socket  96 . In at least one embodiment clip member  51  extends laterally such that when placed within the gap between ends  25  and  27 , a portion is laterally outside the gap. Here, socket  96  (see FIG. 1) may be mounted to the laterally extending portion so that plug  96  resides outside the gap. 
     Clip member  51  forms first and second elongate slots  72  and  74  that are substantially parallel to edges  64  and  66 , respectively, that are closed proximate fourth edge  78  and that are open proximate third edge  76 . With slots  72  and  74  formed as described above, in effect, first and second leg members  68  and  70  are formed that are separated from a body member  62  where leg members  68  and  70  are generally resiliently flexible so that they can be temporarily deformed by pushing inwardly on the distal ends thereof. Hereinafter, the ends of leg members  68  and  70  that are connected proximate fourth edge  78  to body member  62  will be referred to as proximal ends and the unconnected ends of leg members  68  and  70  proximate third edge  76  will be referred to as distal ends. 
     Referring still to FIGS. 2,  3  and  4 , first and second restraining members  84  and  86  extend laterally from the distal and proximal ends of leg member  68  in a direction away from leg member  70 . Similarly, third and fourth restraining members  88  and  90 , respectively, extend laterally and in the same direction from the distal and proximal ends of leg member  70  in a direction away from first leg member  68 . First and second restraining members  84  and  86  have facing surfaces that define a first guide receiving dimension D gr1  where dimension D gr1  is substantially equal to or slightly greater than the guide thickness T g  (see FIG.  6 ). Similarly, third and fourth restraining members  88  and  90  form facing surfaces that define a second guide receiving dimension D gr2  where dimension D gr2  is substantially similar to guide thickness T g . Moreover, referring still to FIG. 3, clip member  51  is dimensioned such that edges  64  and  66  define a clip dimension D clip  substantially equal to the gap dimension D g  illustrated in FIG.  5 . In the embodiment illustrated, the distal ends of leg members  68  and  70  are tapered toward each other so as to form sloped bearing surfaces  80  and  82  which help to facilitate temporary deformation during insertion of member  51  between core ends  25  and  27 . 
     With the core  12  and clip assembly  60  configured in the manner described above with sensor  94  mounted to first side  92 , assembly  60  can be attached within the gap between ends  25  and  27  in the following manner. First, clip member  51  is aligned such that bearing surfaces  80  and  82  are proximate internal surfaces  36  and  38  and, in fact, bear there against. In this case, the edges of surfaces  36  and  38  that surfaces  80  and  82  bear against operate as core bearing surfaces. With clip member  51  so aligned, clip member  51  is forced along a trajectory parallel with passageways  28  and  30  such that force is applied against bearing surfaces  80  and  82  causing leg members  68  and  70  to temporarily flex or deform inwardly toward each other. Eventually, leg members  68  and  70  flex inwardly to the point where restraining members  84  and  88  are forced into and along passageways  28  and  30 . Eventually, restraining members  84  and  88  are forced to the opposite ends of passageways  28  and  30  and extend therefrom. At this point, the deforming force against bearing surfaces  80  and  82  ceases and leg members  68  and  70  resiliently spring back to their original configurations. In this case, edges  64  and  66  are received within passageways  28  and  30  such that restraining members  84  and  86  and  88  and  90  maintain clip assembly  60  within the sensing gap. 
     Referring now to FIGS. 7 through 12, a second embodiment  10 ′ of the invention is illustrated. Many of the components and elements of second embodiment  10 ′ are similar to the components described above with respect to first embodiment  10  and therefore, in the interest of simplifying this explanation, similar elements are identified via similar numbers. Where an element in the second embodiment is similar to one of the elements in the first embodiment yet has some distinction that is meaningful from the perspective of the present invention, that element is identified by the same numeral as the element in the first embodiment above followed by a prime. 
     Embodiment  10 ′ includes a guide core  12 ′ and a clip assembly  60 ′. Core  12 ′, like member  12 , above includes a plurality of members that are formed by stacked laminations to form a conductor receiving space  26 . Members of distinction include the end members  14 ′ and  22 ′ that form facing end surfaces  25 ′ and  27 ′. To this end, referring specifically to FIGS. 11 and 12, instead of forming passageways (e.g.,  28  and  30  in FIG. 5) that traverse the entire thickness T g  of core  12 , ends  25 ′ and  27 ′ form recesses  50  and  51  that are elongate but are closed at their ends. Each of members  14 ′ and  22 ′ has an external surface  35 ,  37  which faces in a direction opposite conductor receiving space  26 . The edge formed by outer surface  35  and surface  25 ′ is tapered inwardly toward recess  53  as illustrated, thereby forming a sloped bearing surface  32 . Similarly, a sloped bearing surface  34  that slopes toward recess  50  is formed at the edge where outer surface  37  and surface  27 ′ converge. Other than these distinctions, members  14 ′ and  22 ′ are substantially identical to members  14  and  22  described above. 
     Referring now to FIGS. 8,  9  and  10 , second clip assembly  60 ′, like clip assembly  60  described above, is substantially rectilinear, is formed of resilient plastic or circuit board material, includes first and second oppositely facing edges  66 ′ and  68 ′, third and fourth oppositely facing edges  76  and  78  that traverse the distance between first and second edges  66 ′ and  68 ′, respectively, and first and second sides  92  and  98  that are formed and fitted to receive flux sensor  94  and a plug socket  96 , (and perhaps other circuitry  100 ), respectively. First and second U-shaped slots  72 ′ and  74 ′ are generally elongate, extending substantially parallel to edges  64 ′ and  66 ′, respectively, and opening concavely toward each other. Each of slots  72 ′ and  74 ′ is closed proximate each of the third and fourth edges  76  and  78 , respectively such that the portions of clip member  51 ′ proximate edges  64 ′ and  66 ′ form leaf springs that are resilient and temporarily deformable. 
     First and second restraining members  84  and  86  extend laterally and in the same direction from opposite ends of edge  64 ′ away from edge  66 ′. As in the case of clip member  51  above, restraining members  84  and  86  form facing surfaces that define a first guide receiving dimension D gr1  that is substantially identical the guide thickness T g  (see FIG.  12 ). Referring still to FIG. 9, third and fourth restraining members  88  and  90  extend laterally and in the same direction from opposite ends of edge  66 ′ and define a second guide receiving dimension D gr2  that is substantially similar to guide thickness T g . 
     Referring again to FIGS. 8 and 9, a first retaining member  69  extends laterally and in the same direction from first edge  64 ′ as does restraining members  84  and  86  and is positioned essentially equispaced from members  84  and  86 . Referring also to FIG. 12, member  69  is positioned such that, when end  25 ′ is received between restraining members  85  and  86 , member  69  is received within recess  50 . In a similar fashion a second retaining member  71  extends from between restraining members  88  and  90  in the same direction as members  88  and  90  from edge  66 ′. Retaining member  71  is positioned along edge  66 ′ such that member  71  is received within recess  51  when end  27 ′ is received between restraining members  88  and  90 . 
     With the clip member  51 ′ and core  12 ′ configured as described above, assembly  60 ′ is mounted securely within the gap formed between ends  25 ′ and  27 ′ in the following manner. First, clip member  51 ′ is positioned such that retaining members  69  and  71  are received on bearing surfaces  32  and  34  with sensor  94  extending downward and into the space between ends  25 ′ and  27 ′. Here the edges of members  69  and  71  that rest on surfaces  32  and  34  are clip bearing surfaces. Next, force is applied to clip member  51 ′ forcing member  51 ′ along a trajectory that is substantially perpendicular to the length of recesses  50  and  53  to drive member  51 ′ down and between ends  25 ′ and  27 ′. When force is applied in this manner, members  69  and  71  bend upwardly and are deformed until members  69  and  71  are aligned with recesses  50  and  53 . Once aligned with recesses  50  and  53 , the force applied to members  69  and  71  substantially ceases and members  69  and  71  resiliently spring back their initial configuration such that members  69  and  71  are received within recesses  50  and  53 . 
     Referring again to FIGS. 1 through 5, it has also been recognized that the core  12  can be dimensioned such that a single clip  60  and a single sensor  94  can be used to sense currents of various magnitudes. To this end, as well known in the art, sensors like sensor  94  are designed to sense flux within a specific range and, if flux is outside the expected range, the sensor will not operate properly. In most applications the current that will pass through a conductor and to be sensed via the inventive assembly will be within an expected current range that can be anticipated. Also, as well known in the art, the amount of flux passing across a core gap given a specific current passing through a conductor that extends through the space  26  is related to the sensing dimension D s . Given a specific current magnitude, a large dimension D s  reduces the flux passing between ends of core  12  while a smaller dimension D s  increases the flux. 
     Thus, the sensing dimension of core  12  can be changed while employing a single clip/sensor configuration to enable the single clip/sensor configuration to be used to sense various current levels. For instance, given a first relatively low anticipated current magnitude within a first expected current range, a first core having a first relatively small sensing dimension D s  may be employed so that the flux that results across the sensing dimension D s  is within the sensor&#39;s optimal sensing range. Similarly, given a second relatively high anticipated current magnitude within a second expected current range, a second core having a second relatively large sensing dimension D s  may be employed so that the flux that results across the sensing dimension is again within the sensor&#39;s optimal sensing range. 
     Importantly, to employ the same clip/sensor configuration in each of these two exemplary cases and in other exemplary cases for that matter, the gap dimension Dg formed by each of the cores would be identical. Thus, for instance, referring again to FIG. 5, in the example above, dimension Dg would be identical for each of the first and second cores while sensing dimension Ds would be smaller for the first core (i.e., where the expected current magnitude is relatively low) than it would be for the second core (i.e., where the expected current magnitude is relatively high). 
     It should be understood that the methods and apparatuses described above are only exemplary and do not limit the scope of the invention, and that various modifications could be made by those skilled in the art that would fall under the scope of the invention. For example, in at least one embodiment the core ends (e.g.,  25 ,  27 ) may form both passageways and relatively deeper recesses within the passageways. In addition, other slot configurations are contemplated. Moreover, while sensor  94  is shown on a side of the clip member facing space  26  which helps to protect the sensor  94 , in some embodiments sensor  94  may be on the outer side of the clip member. Furthermore, the clip member and core may be configured with couplers that enable the clip member to be mounted on a different angle with respect to the guide ends. For instance, in FIG. 1, clip  51  may be rotated 90° so that the leg members  68  and  70  extend toward space  26 . 
     To apprise the public of the scope of this invention, the following claims are made: