Abstract:
A light weight, bobbinless high voltage transformer and igniter module is provided that meets low-cost and high-reliability requirements for automotive HID products. A printed circuit board ( 112 ) serves as a carrier for low voltage electronic components. A high voltage bar core transformer ( 114 ) is held in a cradle ( 130, 130′ ) that accommodates potting material and has a channel ( 160 ) that receives a high voltage wire extending from the transformer for connection with a lead ( 104 ) of an HID lamp ( 100 ). Thin walls ( 210, 212 ) allow the cradle to serve as the cavity for the potting of the transformer. In addition, multi-layer dielectric material is disposed between the primary and secondary windings. Preferably, the primary winding ( 196 ) is a strap that covers a large surface area of the secondary winding ( 192 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This application is related to and expressly incorporates herein by reference commonly-owned U.S. patent application Ser. No. 11/646,009 of Varga, et al., entitled “Lamp Transformer”. Cross-reference is also made to commonly owned U.S. patent application Ser. No. 11/646,213, filed Dec. 27, 2006, entitled “Lamp Igniter Module and Transformer Carrier”; Ser. No. 11/646,009, filed Dec. 27, 2006, entitled “Lamp Transformer”; Ser. No. 11/645,879, filed Dec. 27, 2006, entitled “Lamp Transformer Assembly”; Ser. No. 11/513,777, filed Aug. 31, 2006, entitled “Lamp Transformer”; and, Ser. No. 11/710,751, filed Feb. 26, 2007, entitled “High Voltage Transformer and a Novel Arrangement/Method for HID Automotive Headlamps.” 
         [0002]    This disclosure generally relates to a high voltage transformer and igniter module of the type used in a lamp assembly. More particularly, the voltage transformer assembly and igniter module assembly is of the type typically used in an automotive lamp assembly such as a high intensity discharge (HID) lamp. 
         [0003]    There is a continuing demand for automotive HID lamps. Just as importantly, there is a continued need for addressing various issues with regard to the final product, reliability, and the overall weight of the assembly. For example, manufacturers over the years have improved on the weight of the headlamp assembly in an effort to contribute to the need to decrease the OEM&#39;s desire to reduce the overall weight of an automotive vehicle. Although reductions have been achieved in reaching a weight of approximately 65 grams, further recent improvements in weight reduction have been limited. 
         [0004]    Still another area needing improvement in automotive HID lamps relates to the cost to manufacture. For example, it is important that assembly of the lamp components be repeatable, accurate, and reliable, as well as limiting the number of steps on the manufacturing process. For example, it is important to limit the number of welds required to connect electrical components. Likewise, eliminating handling or processing steps typically results in reduced manufacturing costs. Just as important, however, is the improved quality that results from incorporating precise, repeatable steps into the manufacturing process so that overall quality of the resultant product improves. For example, a separate, special fixture is presently required for potting a lamp transformer of the type shown and described in the Ser. No. 11/646,009 application commonly owned by the assignee of the present application. 
         [0005]    Further, although bobbinless transformer assemblies are generally known in the transformer art, incorporation into the transformer assemblies used in automotive lamp applications presents unique circumstances in still being able to address high voltage insulation factors. For example, a challenge remains in effectively reducing weight but without impacting on the need to properly insulate for high voltage applications of the type encountered in a compact environment such as an automotive headlamp. 
         [0006]    Consequently, improvement is required in reducing weight, improving reliability, limiting manufacturing steps and costs, while providing an improved igniter for a HID headlamp. 
     
    
     BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    A lamp transformer assembly includes a transformer having primary and secondary windings. A carrier is dimensioned to receive the transformer and includes a high voltage wire receiving portion formed therein. 
         [0008]    The transformer may include a bar core without a bobbin. 
         [0009]    A secondary winding is wrapped around the bar core, and a primary winding is wrapped around the secondary winding. Moreover, it is preferred that a single layer or multi-layer dielectric material be disposed between the windings. 
         [0010]    The primary winding is preferably a thin strip or strap having a width substantially greater than a thickness. 
         [0011]    A carrier is modified to easily receive first and second ends of the transformer. 
         [0012]    The carrier in one embodiment accommodates the potting material eliminating use of a separate potting fixture and allowing a one-step potting process by providing thin walls around the transformer. 
         [0013]    The strap design of the primary winding also improves the magnetic coupling of the transformer and allows the primary winding to cover a large section or surface area of the secondary winding. 
         [0014]    A primary benefit resides in the decreased weight of the automotive HID igniter assembly. 
         [0015]    Another benefit is found in the improved handling of the high voltage wire. 
         [0016]    Still another benefit relates to improved magnetic coupling between the primary and secondary windings of the transformer. 
         [0017]    Yet another benefit is realized by using the transformer carrier as the potting fixture. 
         [0018]    Still other features and benefits and advantages are found as will be appreciated from reading and understanding the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an exploded view of a light source or lamp and igniter module assembly. 
           [0020]      FIG. 2  is an elevational view of the assembled light source mounted to the igniter module assembly. 
           [0021]      FIG. 3  is a perspective view of one preferred transformer cradle. 
           [0022]      FIG. 4  is a similar perspective view of the cradle of  FIG. 3  receiving a bar core transformer assembly. 
           [0023]      FIG. 5  is a perspective view showing the lead wires and connections to premolded pins in the cradle of  FIG. 3 . 
           [0024]      FIGS. 6-8  are perspective views of a second preferred cradle assembly without the transformer. 
           [0025]      FIG. 9  is a perspective view of the assembled cradle assembly of  FIGS. 6-8  housing a transformer from the underside as a part of the potting process. 
           [0026]      FIG. 10  illustrates installation of a potted transformer-cradle assembly onto a printed circuit board. 
           [0027]      FIG. 11  shows installation of an assembled igniter module into a housing. 
           [0028]      FIG. 12  shows an igniter module positioned in a housing and insertion of a HID lamp into an associated socket. 
           [0029]      FIG. 13  is an enlarged view of an underside of an igniter module of the type shown in  FIG. 12 . 
           [0030]      FIG. 14  illustrates placement and securing of a bottom plate to the housing. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Turning to  FIG. 1 , there is illustrated a lamp assembly  100  such as a high intensity discharge (HID) lamp or ceramic metal halide (CMH) lamp, the details of which are generally known in the art. These types of lamps produce an arc between spaced electrodes and ionize a pressurized fill enclosed within an arc tube. The pressurized gas fill may or may not include mercury. The spaced electrodes are electrically and mechanically connected to outer leads  102 ,  104  that are, in turn, electrically and mechanically connected to a burner assembly or igniter assembly  110 . The igniter assembly increases or steps up incoming voltage to an elevated level, for example to a level on the order of 25 kV, to provide an instant start for the discharge lamp  100 . 
         [0032]    The igniter assembly includes a printed circuit board assembly  112  that receives a transformer assembly  114  thereon, and which is enclosed within housing  116 , an opposite end of which receives a bottom cover  118  in sealed relation to the housing when assembled. A crown  120  is provided on the housing and preferably includes multiple retaining fingers  122  to mechanically engage one end of the lamp assembly  100 .  FIG. 2  illustrates the assembled lamp assembly with the igniter module assembly  110 . 
         [0033]      FIG. 3  shows one preferred arrangement of a cradle or carrier  130  that is dimensioned to receive a transformer to be described further below. The cradle of  FIGS. 3-5  includes first and second generally parallel members or end walls  132 ,  134 . The end walls are held in spaced, generally parallel relation by interconnecting member(s)  136 . Here, two spaced interconnecting members  136   a ,  136   b  are connected at opposite ends to the end walls  132 ,  134 . Additionally, a transverse support  138  may also be provided to add rigidity to the spaced interconnecting members. It will also be appreciated that the end members, interconnecting members, and transverse member may all be formed as a one-piece arrangement, such as in a molded plastic. This is desirable for ease of manufacturing and since the plastic can also incorporate pins/supports at selected locations for reasons that will become more apparent below. 
         [0034]    First or interior surfaces  132   a ,  134   a  of the respective end members  132 ,  134  are disposed in facing relation. Each interior surface preferably includes a recess  150  that extends inwardly from an arched end of the end member and terminates at a location above the interconnecting members  136 . In addition a through slot  152  is provided in each end member and extends completely through the end member, i.e.,  132   a ,  134   a  to external surfaces  132   b ,  134   b . Moreover, the through slots preferably extend over a limited height of the end members, i.e., less than the height of the recesses  150 . 
         [0035]    An outer surface  134   b  of one of the end members (here, the right-hand end member  134  as shown in  FIGS. 3-5 ), includes a high voltage wire receiving portion or channel  160 . The channel is formed by a raised pair of walls  162 ,  164 . It will be appreciated by one skilled in the art that the channel can be formed in a variety of ways, and likewise adopt a variety of configurations. However, it is desired that the channel  160  have a depth, or stated another way, that the walls  162 ,  164  have a height such that the channel depth is sufficient to fully receive diametrical dimension of a high voltage wire leading from the transformer. 
         [0036]    In addition, an extension portion shown as angled wall  166  extends from a base portion of end member  134  at an area adjacent the interconnecting member  136   a . As will be described further below, the angled member  166  includes a channel on an underside thereof that is in operative communication with channel  160  and terminates at a region generally centrally located between the end walls of the carrier. 
         [0037]    Conductive pins  180  are preferably located in respective corners of the cradle. The pins serve as either a conductive attachment region, for example for the low voltage wire to be described further below, or simply serve as a locating means or support for the cradle relative to the printed circuit board assembly as will also become further evident below. 
         [0038]    As shown in  FIG. 4 , a bar core transformer is received in the cradle. More particularly, the transformer assembly includes a bar core  190 . Wrapped around the conductive core is an insulative material and then is wrapped a relatively thin wire (e.g., on the order of 29 gauge wire) secondary winding  192  that has multiple turns along the length of the bar core. For example, where a prior arrangement may include five layers of secondary windings that would each have one hundred sixty turns total or 53 turns per layer, the present arrangement is substantially less. For example, without limiting the present disclosure, an exemplary arrangement may include only three layers of forty turns in each layer (total number of turns is 120) when used in conjunction with the primary winding of the present disclosure. Preferably, the secondary winding terminates at a location spaced from the end members once the transformer is mounted in the cradle. More particularly, since no bobbin is used in the transformer assembly, margin tape  194  may be provided to hold the secondary windings in place. 
         [0039]    Opposite ends of the bar core of the transformer assembly are received within the recesses  150  of the respective end members  132 ,  134 . This cradle design allows the bar core transformer to be inserted from the arched end of the end members toward the interconnecting members. In addition, a primary winding  196  is shown as a thin strip or strap having a width that is substantially greater than a thickness of the strap. This allows the primary winding to cover a substantial surface area of the secondary winding when wrapped therearound as illustrated. This improves the magnetic coupling between the primary and secondary windings without adding more turns on the secondary winding as would be required if a corresponding thin wire were used for the primary winding. 
         [0040]    In addition, a multi-layer dielectric material is disposed between the primary and secondary windings to serve as an insulation layer between the windings. Moreover, as noted above the transformer does not include a bobbin. Instead, using the single or multi-layer dielectric material allows the conventional bobbin to be eliminated. Thus, reduced weight is achieved by eliminating use of the bobbin, reducing the number of layers and turns of the secondary winding, and without impacting operability of the transformer assembly. 
         [0041]    First and second ends  196   a ,  196   b  of the primary winding pass through corresponding slots  198  in respective interconnecting members  136   a ,  136   b . The ends  196   a ,  196   b  of the primary winding are interconnected to the printed circuit board. 
         [0042]      FIG. 5  is similar to  FIG. 4 , however, low voltage and high voltage wires of the transformer are additionally shown in the assembly. Particularly, a low voltage lead wire  200  extends from a first end of the transformer assembly and passes through the slot  152  in the first end member  132 . The lead wire  200  is routed for interconnection and soldering (i.e., electrically and mechanically connected) to one of the pins  180   a , preferably through a solder interconnection. To provide further support and insulation for this lead wire as it passes through the slot, a dielectric sleeve  202  is received over the low voltage lead wire, at least through the region where the lead wire passes through the slot  152 . 
         [0043]    At the other end of the cradle assembly, a high voltage lead wire  204  extends from the other end of the transformer, passes through slot  152  and is received in the recess  160 . Likewise, the high voltage lead wire preferably has an insulating sleeve along at least a portion thereof where the lead wire passes through the slot  152 . The high voltage lead wire continues through the angled arm  166 , and particularly, as better illustrated in  FIG. 9 , through groove  206  provided in the underside of the angled arm  166 . In this manner, the lead wire is substantially covered or contained as it proceeds from the end of the transformer, along the second end member  134 , and routed to a more central location for connection with the lamp lead and the printed circuit board to be described below. 
         [0044]      FIGS. 6-8  illustrate a second embodiment of a cradle assembly where like elements are identified with like reference numerals with a primed (′) suffix, while new components are identified with new reference numerals. A pair of side walls  210 ,  212  and a continuous bottom wall  214  are provided and interconnect the end members  132 ′,  134 ′ and angled member  166 ′. The transformer has been removed for ease of illustration. As is evident, slot  152 ′ proceeds through the end wall  132 ′, and likewise slot  152 ′ extends entirely through end wall  134 ′. The sidewalls  210 ,  212  and bottom wall  214  form a central cavity  216  dimensioned to receive the transformer when the transformer is slid in along recesses  150 ′ provided along each interior face of the end members. 
         [0045]    As shown in  FIG. 9 , the cradle assembly with the transformer installed therein, is then ready for potting. Selective openings or crevices must be sealed. Particularly, slots  196  that receive opposite ends of the primary winding strap, and the slots  152  provided in each end member are closed or plugged. Once plugged, the cavity  216  is filled with a suitable potting material and cured. In this manner, the cradle assembly essentially serves as the potting fixture so that minimal setup and processing time is required. It will be appreciated that the embodiment of  FIGS. 3-5  will require the cradle with installed transformer to be placed in a separate potting fixture. 
         [0046]      FIG. 10  illustrates the potted transformer/cradle assembly installed on the upper surface of the printed circuit board  112 . The potting sidewalls are not shown in order to permit an illustration of the transformer received in the potting material. Other electrical components, forming no particular part of the present invention, are shown as being electrically and mechanically connected to the printed circuit board. 
         [0047]    The printed circuit board  112  with installed components is tested and, if qualified, the igniter board is then installed into the housing  110 , and particularly into cavity  220  through the lower, open end. A sealant is provided along a connector receiving recess  222  in the housing in order for the connector  224  to be sealingly and securely secured to the housing.  FIG. 11  illustrates complete insertion of the igniter module into the open end of the housing and illustrates how peripheral grooves in the connector  224  are received on either side of the sidewall of the housing to resist pull-out forces and securely position the printed circuit board in the housing. As shown in  FIG. 12 , the end of the high voltage wire  204 , where the high voltage wire exits the groove  206  of the angled arm  166 , is then accurately positioned adjacent the lamp lead  104 . The lamp lead and high voltage transformer wire are then welded or otherwise mechanically and electrically connected, and in addition, the secondary lamp lead that interconnects with the outer lead  102  is welded or otherwise mechanically/electrically connected to the printed circuit board. Thereafter, potting material is used to cover these interconnections. Next, the cover  118  is aligned over the open end of the housing and fusion bonded or otherwise secured along its perimeter to provide a sealed mechanical connection with the housing. 
         [0048]    The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations.