Protective method of support for an electromagnetic apparatus

Abstract: A method of assembling an electromagnetic device having a plurality of magnetic cores (30) with substantially planar bases, by placing the magnetic cores upon a fixture (18) adapted to align the planar bases of the magnetic cores (30) in a coplanar relationship, applying a resilient adhesive along a core receiving (34) side of a bracket (12), placing the bracket (12) over the magnetic cores (30), pressing the bracket (12) down upon the cores (30) until the bracket's coplanar feet (40) contact the fixture (18), removing the bracket (12) and cores (30) from the fixture (18), affixing a thermally conductive elastomeric pad (14) along the coplanar bases of the magnetic cores (30), and fastening the coplanar feet (40) to a thermally conductive plate (16) so as to uniformly compress the elastomeric pad (14) between the plate (16) and the coplanar bases of the magnetic cores (30) thereby providing a thermally efficient and shock resistant support mechanism.

Description: The present invention relates to an automotive electromagnetic apparatus, and more specifically, to a protective method of support for such an apparatus. In the development of an electronic automotive vehicle many problems invariably arise. One set of problems is associated with the use of an electromagnetic apparatus in a vehicular environment. An electromagnetic apparatus has magnetic cores. These magnetic cores generate heat which must be dissipated. One way of cooling an electromagnetic device is to place the magnetic cores of the apparatus in direct contact with a metallic heat sink. The heat sink acts to draw heat away from the cores, and thereafter dissipate the heat. However, in a vehicular environment such an arrangement is undesirable. The magnetic core, a sintered powder metal iron, is very brittle and will crack and chip under very low stresses. Placing the magnetic cores in direct contact with a metallic heat sink can cause damage to and possible failure of the core. Using such an arrangement in harsh vibrating environments as found in automotive vehicles only exacerbates this problem. One approach to remedy this problem is to apply a thermally conductive elastomeric pad to the base of the cores prior to placing them in contact with the heat sink. However, this may create other problems. The manufacture of magnetic cores is a very inexact science in which the height of the cores may vary ±2.0 mm. In order to have a thermally efficient heat transfer between the heat sink and the cores, it is preferred that the bases of the cores be equidistant from the heat sink. The high tolerance associated with the manufacture of the cores makes aligning the bases of the cores prior to applying the elastomeric pad a cumbersome and inexact process. Accordingly, it is seen that a need exists in the art for a protective method of support for an electromagnetic apparatus which insulates the magnetic cores from damage due to vibration while providing efficient cooling of the cores. US patent 5 469 124 already describes a method of assembling a transformer for use in an electronics module of an electric vehicle. The transformer is assembled from the top down by wrapping windings round a thermally conductive hollow coil form and inserting a lower E-core in a first open end of the coil form. An upper E-core is inserted in a second open end of the upper portion of the coil form so that the side legs and centre legs of the upper and lower E-cores are mutually aligned. The thermally conductive coil form has a portion that touches a cold plate when the transformer is mounted on the cold plate. The transformer is secured to the cold plate by a mounting bracket and a thermally conductive compressible material is located between the bottom of the lower core and the top of the cold plate. According to the present invention, there is now provided a method of supporting an electromagnetic apparatus having a plurality of magnetic cores, the magnetic cores being adapted to receive a transformer, the method comprising the steps of: placing a bracket over the magnetic cores in partially surrounding relationship, the bracket having a top portion with a core receiving side and a plurality of leg portions with outwardly projecting feet extending a predetermined distance beyond the magnetic cores; affixing a thermally conductive elastomeric pad to the cores, the elastomeric pad having a substantially planar pad surface; and attaching the bracket feet to a thermally conductive plate so as to uniformly compress the elastomeric pad providing a thermally efficient and shock resistant support mechanism; characterised in that; the magnetic cores are adapted to receive a transformer and a plurality of inductors, the plurality of magnetic cores have substantially planar bases that are aligned in coplanar relationship upon a planar fixture surface of a fixture thereby to form a coplanar base surface such that tolerance variance of the cores is realised on the distal surface of the cores; the bracket has coplanar feet extending a predetermined distance beyond the coplanar bases of the magnetic cores; and the method includes the further steps of; removing the bracket and cores from the fixture; affixing the elastomeric pad to the coplanar bases of the cores, the elastomeric pad having a substantially planar pad surface parallel to the coplanar feet and the coplanar bases, the planar pad surface extending a predetermined distance beyond the coplanar bases of the magnetic cores; and the method includes the step of attaching the coplanar feet to the conductive plate so as to uniformly compress the elastomeric pad between the plate and the coplanar bases of the magnetic cores. The present invention may further include the step of applying a resilient adhesive along the core receiving side of the bracket so as to fasten the bracket to the magnetic cores. An advantage of the present invention is that the support method provides the electromagnetic apparatus with a thermally efficient cooling and shock resistant support structure. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a fixture for an electromagnetic apparatus; Figure 2 is a perspective view of an electromagnetic apparatus placed upon a fixture according to the present invention; Figure 3 is a perspective view of a bracket for an electromagnetic apparatus according to the present invention; Figure 4 is a perspective view of a bracket mounted upon an electromagnetic apparatus utilising a fixture according to the present invention; Figure 5 is perspective view of an electromagnetic apparatus support mechanism with a base mounted elastomeric pad according to the present invention; and Figure 6 is a perspective view of an electromagnetic apparatus support mechanism mounted upon a thermally conductive plate according to the present invention. Turning now to the drawings, and in particular to Figures 5 and 6 thereof, an electromagnetic apparatus support mechanism 10 is shown. The support mechanism 10 has a bracket 12, an elastomeric pad 14, and a thermally conductive plate 16. The support mechanism 10 is assembled utilising a fixture 18 as shown in Figure 1. As shown in Figure 1, the fixture 18 is substantially rectangular and has a planar fixture surface 20. A planar base receiving surface 22 is located central to the fixture surface 20. The base receiving surface 22 is elevated a predetermined distance above and parallel to the fixture surface 20. As shown in Figure 2, an electromagnetic apparatus may have a pair of inductors 26, a transformer 28, and a plurality of magnetic cores 30. The manufacturing tolerances of the cores 30 may be as high as ±2.0 mm. Each inductor 26 and the transformer 28 has a corresponding magnetic core 30. The bracket 12, as shown in Figure 3, has a planar top portion 32 and a core receiving side 34. Projecting downward from the top portion 32 are flanges 35 which are adapted to receive the magnetic cores 30, and thereby restrict lateral movement of the cores 30. Also projecting downward from the top portion 32 are a plurality of leg portions 36 of equal, predetermined length. The leg portions 36 have inwardly directed flanges 38 which are also adapted to receive the magnetic cores 30. Projecting outward of the leg portions 36 are a plurality of coplanar feet 40. The feet 40 have holes 42 therein for receiving a conventional fastener, such as a screw (not shown), therethrough. As shown in Figure 5, an elastomeric pad 14 is formed in a substantially rectangular shape with a predetermined thickness. The pad 14 has a planar adhesive surface 15 and a planar base surface 17 parallel to the adhesive surface. The pad 14 is preferably thermally conductive. As shown in Figure 6, the thermally conductive plate 16 is substantially rectangular with an upper, electromagnetic apparatus receiving surface 19. The plate 16 has fastener receiving holes (not shown) which are adapted to align with the holes 42 of the bracket 12 during assembly. The plate 16 is preferably made out of a metal with high thermal conductivity such as aluminium. In assembly, the fixture 18 of Figure 1 is placed on a flat surface. As shown in Figure 2, the magnetic cores 30 are then placed and aligned on the base receiving surface 22 of the fixture 18 and bonded together in conventional fashion. The bases of the magnetic cores 30 thereby form a coplanar base surface such that any tolerance variance of the cores 30 is realised on the top side. A resilient adhesive, such as a silicon adhesive (not shown), is then applied to the core receiving side 34 of the bracket 12 as shown in Figure 3. As shown in Figure 4, the bracket 12 is then placed over the magnetic cores 30 so that the feet 40 come into coplanar contact with the planar fixture surface 20. This contact insures that the coplanar feet 40 extend a predetermined distance beyond, and are parallel with, the coplanar bases of the magnetic cores 30. After the adhesive cures affixing the bracket 12 to the magnetic cores 30, the assembly is removed from the fixture 18. As shown in Figure 5, the planar adhesive surface 15 of the elastomeric pad 14 is then brought into contact with the bases of the magnetic cores 30. The planar base surface 17 of the pad 14 extends a predetermined distance beyond, and is parallel with, the coplanar bases of the magnetic cores 30 as well as the coplanar feet 40. As shown in Figure 6, the holes 42 of the feet 40 are aligned with the fastener receiving holes of the upper receiving surface 19 of the thermally conductive plate 16. A conventional fastener is then used to attach the bracket 12 to the plate 16. As the fasteners are tightened the pad 14 is uniformly compressed between the bases of the magnetic cores 30 and the plate 16. The resulting electromagnetic apparatus support mechanism 10 is advantageous for a number of reasons. First, the only points of contact of the magnetic cores 30 are with the resilient adhesive of the bracket 12 and the elastomeric pad 14. This arrangement provides a protective cushion for the brittle magnetic cores 30 and helps to prevent cracking and chipping. Second, the coplanar bases of the magnetic cores 30 are in a coplanar relationship and they are parallel with the planar base surface 17 of the pad 14 as well as the coplanar feet 40 of the bracket 12. Thus, upon fastening of the bracket 12 to the plate 16, the pad 14 is evenly compressed and the bases of the magnetic cores 30 are thereby parallel to, and equidistant from, the plate 16. This arrangement provides an even and efficient thermal transfer between the cores 30 and the plate 16 via the pad 14.

Claims: A method of supporting an electromagnetic apparatus having a plurality of magnetic cores (30), the magnetic cores (30) being adapted to receive a transformer (28), the method comprising the steps of: placing a bracket (12) over the magnetic cores in partially surrounding relationship, the bracket (12) having a top portion (32) with a core receiving side and a plurality of leg portions (36) with outwardly projecting feet (40) extending a predetermined distance beyond the magnetic cores (30); affixing a thermally conductive elastomeric pad (14) to the cores (30) , the elastomeric pad (14) having a substantially planar pad surface; and attaching the bracket feet to a thermally conductive plate (16) so as to uniformly compress the elastomeric pad providing a thermally efficient and shock resistant support mechanism; characterised in that ; the magnetic cores (30) are adapted to receive a transformer (28) and a plurality of inductors (26), the plurality of magnetic cores (30) have substantially planar bases that are aligned in coplanar relationship upon a planar fixture surface (20) of a fixture (18) thereby to form a coplanar base surface such that tolerance variance of the cores is realised on the distal surface of the cores (30); the bracket has coplanar feet (40) extending a predetermined distance beyond the coplanar bases of the magnetic cores (30); and the method includes the further steps of; removing the bracket (12) and cores (30) from the fixture (18); affixing the elastomeric pad (14) to the coplanar bases of the cores (30), the elastomeric pad (14) having a substantially planar pad surface parallel to the coplanar feet and the coplanar bases, the planar pad surface (17) extending a predetermined distance beyond the coplanar bases of the magnetic cores (30); and the method includes the step of attaching the coplanar feet to the conductive plate (16) so as to uniformly compress the elastomeric pad between the plate (16) and the coplanar bases of the magnetic cores (30). A method according to claim 1, wherein the fixture (18) has a planar fixture surface (20) and a central planar portion (22) elevated a predetermined distance above and parallel to the planar fixture surface (20). A method according to claim 2, wherein the predetermined distance above the planar fixture surface (20) is equal to the predetermined distance the feet (40) extend beyond the coplanar bases of the magnetic cores (30). A method according to claim 1, 2 or 3, wherein the bracket (12) further includes inwardly projecting flange portions (35) adapted to receive the magnetic cores (30). A method according to any one of the preceding claims, including the further step of applying a resilient adhesive along the core receiving side of the bracket (12) so as to fasten the bracket (12) to the magnetic cores (30) in supportive and shock absorptive fashion.

Inventors: HUSS JOHN BERNARD, HUSS, JOHN BERNARD
Applicants: FORD MOTOR CO, FORD MOTOR COMPANY
Application year: 1998
Main classification: H01F41
IPC codes: H01F41, H01F27