Patent Document

TECHNICAL FIELD 
     The present disclosure relates to a sensor assembly and method of making the same. More particularly, the present disclosure relates to connecting a spool assembly containing the sensor element to a harness assembly. Still more particularly, the present disclosure relates to a sensor assembly, wherein electrical interaction between the spool assembly and the harness assembly results in elimination of an over-mold interface between the harness assembly and a housing in which the spool assembly is disposed. 
     BACKGROUND OF THE INVENTION 
     Virtually all such sensors are of the magnetic type, either variable reluctance or galvanomagnetic (e.g. Hall generators or magnetoresistors). Galvanomagnetic or digital sensors are becoming progressively more preferred due to their capability of greater encoding flexibility and speed independent output signals. Magnetic sensors operate on the principle of detecting magnetic flux density modulation caused by the movement of appropriately configured reluctors (or targets). 
     Variable reluctance (VR) sensors and digital sensors are commonly designed having an integral harness assembly. The harness assembly includes a connector assembly at one end for operable electrical connection as an input and a grommet that is over-molded to the wiring harness having leads extending therefrom at an opposite end for operable electrical connection with a sensor element of a spool or holder assembly. The spool assembly is then disposed within a sensor housing or cap. 
     Prior art sensor assemblies having harness leads extending from the harness assembly are typically crimped to leads extending from the spool assembly for electrical connection therewith. The sensor housing or cap open at one end is then slid over the spool assembly resulting in a subassembly that is then over-molded to form an over-molded seal cover. The over-molded seal cover is disposed over a perimeter of both the cap and grommet to seal the crimped electrical interface between the grommet and the spool assembly by sealing the open end of the cap with the over-mold grommet. After the subassembly is over-molded, brackets, o-rings, clips, and the like may be added to complete the sensor assembly. 
     With regard to production of an integrated assembly, the prior sensors have presented some challenges. In particular, VR and digital sensors include a large number of delicate parts that must be maintained in a connected state during packing in a housing. The crimped wire connections between components are particularly fragile. The crimped wire connections have been known to break easily during over-molding, as a result of thermal stress, thermal cycling and/or vibration during servicing and for other reasons. Over-molding a sensor having 40 gauge wire is a primary cause of stress that the sensor experiences and can also accelerate failures in less than desirable soldered and crimped terminal connections. In addition, the difference in thermal coefficients of expansion between the plastic, coil wire, harness and crimped terminal connections may cause the sensor to fail prematurely in the field 
     It would be desirable to have a sensor assembly that would overcome the above disadvantages without involving extra steps and expense. 
     SUMMARY OF THE INVENTION 
     A sensor package and method of manufacturing for magnetic sensing in a vehicle is disclosed. In an exemplary embodiment, a sensor package includes a holder assembly having two sensor terminals extending therefrom. The sensor terminals are in electrical communication with a sensor element configured for electromagnetic sensing. The holder assembly is configured for disposing the sensor element therewith. A harness assembly includes a connector at one end for connection with another device and a harness head at an opposite end in electrical communication with the connector. The harness head includes two harness terminals extending therefrom configured for electrical communication with the corresponding sensor terminals. The sensor package also includes a means for snap-fit assembly between the holder assembly and the harness head. The sensor package further includes a sensor housing having a cavity for receiving a sensor subassembly therein, the sensor subassembly including the holder assembly assembled with the harness head. The sensor housing has a sealable interface with the harness head. The sealable interface is configured to admit and secure the sensor element therein and provide protection from an outside environment. 
     In another embodiment, a method for manufacturing a sensor package is disclosed. The method includes: configuring a harness head having a pair of harness terminals extending therefrom for operable electrical communication with a sensing element and configuring a holder assembly to maintain the sensing element in a lower portion of the holder assembly and maintain a pair of sensor terminals extending from an upper portion of the holder assembly; the pair of sensor terminals are in electrical communication with the sensing element. The method further includes configuring the harness head and holder assembly with a corresponding means for snap-fit assembly to each other and connecting the pair of harness terminals with the pair of sensor terminals. A sensor housing is configured to seal the sensing element and the connected terminals from an outside environment. A resultant subassembly having the harness head assembled with the holder assembly is inserted into the sensor housing and harness head is heat-staked with the sensor housing to fix the subassembly relative to the sensor housing. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following brief description of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the exemplary drawings, which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several figures: 
     FIG. 1 is an exploded perspective view of a VR sensor assembly according to one embodiment of the present disclosure; 
     FIG. 2 is an exploded perspective view of a digital sensor assembly according to another embodiment of the present disclosure; 
     FIG. 3 is an enlarged partly perspective view of FIG. 1 illustrating a snap-fit connection features between a spool assembly and an over-molded head of a harness assembly; 
     FIG. 4 is a perspective view of the over-molded head of FIG. 3 illustrating the snap-fit connection in more detail and a pair of terminal pockets; 
     FIG. 5 is a front view of the spool assembly and the over-molded head of a harness assembly shown in FIG. 3 illustrating connection therebetween; 
     FIG. 6 is a side view of the spool assembly and the over-molded head of a harness assembly shown in FIG. 5; 
     FIG. 7 is a perspective view of an assembled VR sensor shown in FIG. 1; and 
     FIG. 8 is a perspective view of an assembled digital sensor shown in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the Drawings, FIGS. 1 and 2 generally depict two exemplary embodiments of a sensor assembly  10  according to the present disclosure, wherein the sensor assembly  10  serves to eliminate an overmold interface proximate terminal leads between a harness assembly  12  and spool or holder assembly  14  for electrical connection therebetween, which is subject to failure when prior art sensor assemblies involve subsequent over-molding in this region. In this regard, subsequent over-molding in the prior art is replaced by heat staking a sensor housing or cap  16  to a harness head  18  of harness assembly  12  to seal the sensor element from the outside environment. 
     Sensor assembly  10  in FIG. 1 is a VR sensor assembly  10 . Sensor assembly is composed of a subassembly including harness assembly  12 , spool assembly  14 , and cap  16 . A bracket  20  and o-ring  22  is disposed around cap  16  after the subassembly is completed for mounting the completed sensor assembly within a substrate bore (not shown), such as a transmission case bore for sensing the velocity of a transmission gear, for example. More specifically, bracket  20  includes a mounting hole  24  at one end for receipt of a mechanical fastener such as a bolt or stud with a complementary nut to secure bracket  20  relative to a horizontal surface of an engine block, for example. Bracket  20  is configured at an opposite end for location within and crimping engagement with a groove  26  configured in cap  16 . This not only ensures that the sensor assembly  10  will remain permanently associated with respect to bracket  20 , but further ensures the orientation of the sensor assembly with respect to the reluctor or target (not shown) will be correct. It is to be understood that those ordinarily skilled in art may utilize any known modality to trap and/or permanently orient the sensor assembly with respect to the bracket, and that the various views of the present disclosure are by way of exemplification and not limitation. 
     Cap  16  is further configured with a second groove  28  for receiving and retaining o-ring  22  therein. O-ring  22  is configured to seal cap  16  in a bore in which it is disposed for limiting passage of fluids thereby that may be hostile to the-components of sensor assembly  10 . 
     Still referring to FIG. 1 in conjunction with FIG. 3, spool assembly  14  includes spool body  30  having a pair of L-shaped terminals  32  molded therein and extending from a top surface  34  thereof. A vertical portion  35  of each L-shaped terminal  32  extends from top surface  34  while a horizontal portion  36  of each L-shaped terminal  32  extends from an intermediate portion of spool body  30  extending substantially perpendicular to vertical portion  35 . Although terminals  32  have been described as substantially L-shaped terminals, other suitably shaped terminals  32  are contemplated. Spool body  30  includes a lower portion  38  having a coil  40  wound around spool body  30 . Ends  42  of coil  40  terminate with electrical connection with a corresponding horizontal portion  36  of L-shaped terminals  32 . 
     Referring now to FIGS. 1 and 2 in conjunction with FIG. 3, spool assembly  14  in FIG. 1 is alternatively replaced with holder assembly  14  in FIG. 2 for a digital sensor assembly  10 . An active sensor package or element  40 , can be received in a lower end of holder assembly  14 . The active sensor is a sensor that includes a solid-state chip for sensing changes in a magnetic field. Examples of active sensors include Hall effect sensors, MR sensors and the like. An optional capacitor  44  (shown in FIG. 2) can be located in a slot in the upper end of the holder assembly  14  adjacent the terminals  46 ,  48  extending from active sensor  40 . The capacitor is bridged across the terminals  46 ,  48 . It will be noted that although holder assembly  14  and harness head have been disclosed as separate pieces of sensor assembly  10 , holder assembly  14  and harness head  18  are optionally configured as an integral one piece assembly. 
     Harness assembly  12  is composed of a connector body  50  at one for connection as an input device to another device, such as a control module, for example. Connector body  50  is preferably moldably configured with terminal tabs  52  extending at one end and a wiring  54  electrically connected to corresponding tabs  52  extending from another end of connector body  50 . 
     Harness assembly  12  is further composed of harness head  18  over-molded to wiring  54  opposite connector body  50 . Harness head  18  is over-molded having harness head terminals  56  electrically connected with wiring  54  corresponding to tabs  52  of connector body  50 . Head terminals  56  extend from harness head  18  for operable electrical connection with corresponding terminals  32  extending from spool or holder assembly  14 . Harness head  18  further includes an internal o-ring groove  58  for receiving and retaining an internal o-ring  60 . O-ring  60  is configured to form a seal between harness head  18  and an inside portion of cap  16  to isolate the electrical connection of harness assembly  12  with spool or holder assembly  14 . 
     Referring now to FIGS. 3 and 4, operable connection of spool assembly  14  with harness assembly  12  is described in more detail. In an exemplary embodiment, harness head  18  further includes four prongs  64  extending from a bottom surface  66  of head  18 . The four prongs  64  are arranged on a perimeter defining bottom surface  66 . Each prong includes a means for engaging a corresponding means extending from a top surface  34  of spool assembly  14  for locking engagement between harness assembly  12  and spool assembly  14 . In an exemplary embodiment, the means includes a snap feature  68  extending from each prong  64  facing a corresponding snap feature  68  extending from an adjacent prong  64 . Snap features  68  extending from two adjacent prongs  64  lockingly engage with a latch feature  70  extending from top surface  34  of spool assembly  14 . Each latch feature  70  is aligned to latch with two corresponding prongs  64 . In an exemplary embodiment shown in FIG. 3, latch feature  70  is configured having two hooks  72  opposing each other. Each hook  72  is configured to receive and then latch with a corresponding snap feature  68 . Each latch feature  70  having hooks  72  defining outboard sides of each latch feature  70  includes a space  73  configured therebetween to allow resilient movement of hooks  72  during snap lock engagement with corresponding snap features  68  on corresponding prongs  64 . 
     It will be recognized by one skilled in the art that snap features  68  and latch features  70  are configured to cooperate in snap-fit assembly. For example, a periphery of bottom surface  66  of harness head  18  may include a plurality of snap-fit connectors, preferably resilient, ribs, teeth, grooves, flanges, and the like to cooperate in a snap-fit arrangement with a complementary configured latch feature  70  on top surface  34  of spool assembly  14 . In addition, it will be noted that at least one of latch feature  70  and snap feature  68  may optionally be resilient to facilitate connection, while making difficult disconnection therebetween. 
     Referring now to FIG. 4, bottom surface  66  of harness head includes two terminal pockets  74  configured and aligned to locate terminals  32  extending from top surface  34  of spool assembly  14 . Terminal pockets  74  are proximate terminals  56  extending from bottom surface  66  of harness head  18 , such that terminals  56  are slidably connected to corresponding terminals  56  as harness head  14  is engaged with spool assembly  14  via the means for such lockable engagement discussed above. 
     Referring now to FIGS. 5 and 6, harness head  18  is illustrated as being assembled to spool assembly  14 . It will be recognized in this assembled state that terminals  56  and  32  are exposed as a result of an opening  76  provided between prongs  64 . Opening  76  allows enough space to provide resistance welding of corresponding terminals  32 ,  56 . By resistance welding terminals  32  and  56 , the need to crimp terminals together is eliminated and replaced by a more robust process. 
     Referring now to FIGS. 1-8, after snap-fit engagement between harness assembly  12  and spool assembly  12  and subsequent resistance welding of terminals  32 ,  56 , a resultant subassembly  80  shown in FIGS. 5 and 6 can be inserted through an opening  82  in cap  16 . Opening  82  is defined by an upper wall  84  defining an upper portion of cap  16 . Opening  82  is further defined by a notch  86  configured in upper wall  84 . Notch  86  is configured to align with a complementary configured anti-rotation feature  88  extending from a flange  90  of harness head  18 . Anti-rotation feature  88  prevents movement of subassembly  80  with respect to cap  16 . Furthermore, harness head  18  is configured with at least one heat-stake groove  92  aligned with a corresponding heat stake groove  94  configured in upper wall  84  of cap  16 . In an exemplary embodiment as depicted, two corresponding and complementary heat-stake grooves  92 ,  94  are configured in harness head  16  and upper wall  84 , respectively. Heat stake-grooves  92 ,  94  are configured to hold a heat-stake that is applied upon assembling subassembly  80  with cap  16 . 
     Referring now to FIGS. 7 and 8, flange  90  of harness head  18  is configured to complete the top of a resulting completed sensor assembly  10  with the aid of o-ring  60  forming a seal to seal the outside environment from entering into the sensor cavity defined by cap  16 . Once cap  16  and harness head  18  of harness assembly  12  are heat-stacked, there is no need for over-molding as in the prior art. 
     Referring again to FIGS. 1-3, the components of sensor assembly  10  are assembled as follows. First, harness head  18  of harness assembly  12  is aligned with spool or holder assembly  14  for connection therewith. More specifically, the terminals  32  are aligned with terminal pockets  74  on bottom surface  66  of harness head  18  and snapped into the corresponding snap retention features  68  and  70 . The leads  32 ,  46 ,  48  of the sensor element package, and optionally the capacitor in an active sensor element package, can be resistance welded to the terminals  56  extending from the harness head  18  or attached and electrically connected by any appropriate known method. The advantage of the present arrangement includes the relatively robust connection between terminals  32 ,  46 ,  48  and  56 , which is not possible with crimping terminals of the prior art. 
     Next, the resulting subassembly of the connected harness assembly  12  and spool/holder assembly  14  is inserted into sensor housing or cap  16  and heat-staking harness head  18  to an upper portion of cap  16  using corresponding heat-stake grooves  92 ,  94 . In an exemplary embodiment, the harness head and cap are fabricated with a thermoplastic material. The molded thermoplastic material seals the sensor cavity from the outside environment by molding flange  90  and anti-rotation feature  88  extending from flange  90  of harness head  18  to align and cover cap  16  defining opening  82  thereof. The molded thermoplastic material also seals the sensor cavity from the outside environment with help from o-ring  60  to seal a gap formed between a bore defined by cap  16  and an outside surface of harness head  18 . In a preferred embodiment, harness head  18  includes a circumferential channel  58  configured therein to retain o-ring  60 . 
     The above described sensor assembly and method of manufacture eliminate the over-molding process by placing the cap over the spool or holder assemblies that have been previously snapped to the harness assembly by snap-fit engagement means that also provides suitable space for subsequent resistance welding of the terminals therebetween. The resultant subassembly is disposed within a cap for heat-staking the cap to the harness assembly. The above disclosed nonover-mold concept allows VR and digital sensors to be produced using similar designs, tooling, and processes. 
     Accordingly, the above described sensor device and method of manufacturing afford simple and cost effective means to assemble a sensor body with a housing and harness assembly eliminating any need for an over-mold interface proximate crimped electrical terminals and over-molding the subassembly associated with coupling the harness assembly with the housing or cap. In addition, such means of assembling the sensor assembly prove to extend the longevity thereof by eliminating an over-mold interface proximate crimped electrical connections and thin magnetic coil wire subject to premature failure with such subsequent over-molding. The above described sensor device and method of manufacture allows for VR sensors and digital sensors to be developed using similar designs, tooling, and processes. By employing a nonover-mold engagement with a harness assembly in conjunction with a sensor assembly, simplicity, timesavings, cost savings, and reliability can be gained. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

Technology Category: 3