Insert moulded terminal for alternator

Abstract: An improved terminal for electrical connection to an alternator includes a connecting plate (60) formed as portion of a radiator plate (49) including recesses adapted to receive diodes (30) for use in forming a rectifier bridge. The rectifier bridge assembly (42) comprises a plastic housing that is insert moulded over the radiator plate (49) including louvres for passing cooling air past the diodes. The connector plate (60) includes an opening (62) to receive the stem (66) of an enlarged headed fastener (64) before the plastic body is formed around the radiator plate. Before moulding, the bolt (64) is pressed by a mould insert (78) against the contact plate so the stem (66) extends outwardly within an axially extending, circumferentially interrupted wall formed by the moulding process. The outer surface of the connecting plate (60) includes an axially raised surface at the periphery of the opening and an adjacent tapered surface so that a mould insert pressed against the connecting plate keeps it free of plastic during the moulding process, and any overruns of moulding material against the tapered surface remain retracted from the axially extended contact surface.

Description: The present invention relates generally to the field of alternators as used, for example, to supply DC electrical power to motor vehicles and, more particularly, to an improved alternator rectifier bridge assembly with improved electrical output terminals and a method of making the improved assembly. A three-phase alternator rectifier bridge, such as used in a motor vehicle alternator, comprises three "negative" diodes having their anodes connected to a ground terminal and three "positive" diodes having their cathodes connected to a voltage output terminal. Each of the cathodes of the negative diodes are connected to one of the anodes of the three positive diodes and to one of three stator windings of an alternator. The diodes used to form rectifier bridge circuits have been packaged together as a unit which preferably is mounted within the housing of the alternator. For example, U.S. Patent No. 3,184,625 describes a technique for mounting diodes on metal plates within the housing of an alternator but requiring numerous wire-to-wire solder connections to interconnect the diodes in the rectifier unit. A problem created and addressed in known prior art rectifier bridge circuits is the dissipation of heat which is generated by the conduction of substantial currents through the diodes of the bridge circuits. U.S. Patent Nos. 3,539,850, 3,925,809, 3,959,676, 4,218,694, 4,307,437, 4,321,664, 4,538,169, 4,799,309 and 4,835,427 all show various techniques for packaging diodes in a manner that will facilitate heat dissipation. The previous U.S. Patent No. 5,043,614, discloses a method and structure for assembling an alternator rectifier bridge incorporated into an alternator housing. Half of the diodes of the rectifier bridge are inserted into apertures formed into an alternator housing end plate such that the end plate serves as one output for the alternator and also as a massive heat sink to dissipate heat generated in the diodes. Typically, the diodes inserted into the end plate are negative diodes with their anode electrodes being inserted and their cathode electrodes extending beyond the end plate. The other half of the diodes of the rectifier bridge are inserted into apertures formed in a radiator plate. Typically, the diodes inserted into the radiator plate are positive diodes with their cathode electrodes being inserted and their anode electrodes extending beyond the radiator plate. The radiator plate is embedded into a plastic circuit member together with conductor members which serve to interconnect electrodes of the diodes and connect the diodes to stator windings of the alternator. The conductor members also provide other electrical connections required for efficient manufacture and proper operation of the alternator. Although the patented radiator plate has improved heat dissipation abilities over previously known multiple component bridge circuit assemblies, the terminals formed with the radiator plate for connection as an output terminal to a conductor were formed as spade terminals. However, the connection between the fork-shaped female terminal which dovetails with the spade-shaped male terminal has limited current carrying capability. Moreover, modern vehicles have more load circuits, and alternators are accordingly built to produce substantially higher currents. Furthermore, the clamping force of the female member must be limited to allow insertion of the spade shaped male terminal. Any looseness in the connection increases the resistance of the terminal, and in view of the high current flowing from the alternator, substantially increases the heat generated at the coupling. Moreover, the more heat generated at the coupling, the higher the resistance of the connection. As a result, an ever increasing cycle or runaway of increasing heat and resistance can adversely affect the electrical system and the coupling. Previously known couplings which provide a secure connection between mating parts often employed a threaded fastener specially constructed for mounting and threadably engaging electrical terminals against each other. However, while such fastener carries higher clamp loads, and therefore can carry higher currents, such structures are difficult to manufacture, install and assemble, and can employ numerous component parts such as insulating shells and machined supports. One previously known connection included a bolt extending through a plastic insulating sleeve inserted through an alternator housing portion. A first nut tightened against the end of the sleeve supported the harness eyelet for engagement by a second nut threadedly engaged on the bolt against the eyelet and the first nut. However, the effect of changing temperature, ageing and environmental conditions on the different materials could cause loosening of the electrical connection as the nuts separated. Another previously known alternator construction with end plates supporting a rectifier bridge assembly required a specially constructed bolt mounted for contact with the positive diode plate by a knurled peripheral portion in wedging engagement to the plate, and a threaded portion for threadably engaging a nut. In addition, a threaded boss area extended through an insulating housing to engage a boss with a flared flange retaining a washer on the boss. The boss was threadably engaged with the bolt once the knurled portion had been embedded in the rectifier assembly to provide a flat surface against which terminals and a nut could be tightly engaged to complete a secure connection for output from the alternator. However, the manufacturing and assembly difficulties render the alternator construction very expensive. Since other previously known bolt and nut connections, may not be efficient conductors. Previous practice required the bolt to be fabricated of more expensive material with better conductivity, such as a copper stud, which is required to be larger for strength. Furthermore, the loose connection problems discussed above could be encountered with such a structure. GB-A-2 235 822 discloses a rectifier assembly for motor vehicle alternators having positive and negative diodes respectively inserted by their housings into two metallic, mutually parallel cooling plates between which is disposed a printed circuit board for connecting the diodes to one another as well as to wires of a stator winding of the alternators. On the front, positive cooling plate, there is a radially outwardly guided positive terminal which comprises a retaining plate and a bolt , which is fastened thereto and projects radially beyond the cooling plates. The retaining plate is riveted by spaced rivets onto the front cooling plate and a plastics part is formed onto the outer edge of the circuit board to accommodate the limb of the retaining plate. According to the present invention, there is provided a rectifier bridge assembly as set forth in Claim 1 of the appended claims. The plastics circuit member adapted to be secured to the end plate is insert moulded about the radiator plate, preferably in the manner taught in U.S. Patent No. 5,043,614. The connecting plate portion is preferably bent to a position perpendicular to the radially extending arms of the radiator plate so that the axis of the opening lies on a plane parallel to the axially extending arms. A fastener is then inserted through the opening, preferably, the radiator plate is inserted in a mould. As the mould is closed, a mould insert fixes the position of the fastener against the connector plate, and another mould part rests against the opposite side of the connecting plate to prevent the mould material from covering the exposed surface of the connector plate adjacent the threaded stem of the fastener. As a result, the present invention provides a more secure electrical connection for conductors used to output electrical signals generated by the alternator. In addition, the invention provides an electrical connector which is substantially easier to manufacture and assemble than previously known secure connectors by utilising the moulded plastic body as a support for the fastener and to form an insulating body around the fastener. Furthermore, the connecting plate portion of the radiator plate is engaged directly against a harness eyelet between the nut and the enlarged fastener head, whereby the fastener need not be used as a conductor. The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of the electrical circuit of an alternator rectifier bridge circuit; Figure 2 is a perspective view of a portion of an alternator rectifier bridge construction in accordance with the present invention; and Figure 3 is an enlarged sectional view of a portion of the alternator construction shown in Figure 2. Referring first to Figure 1, a typical alternator bridge circuit 10 connected to stator windings 12, 14, 16 of an alternator. The bridge circuit 10 may be used with any type of alternator, but is particularly applicable to three-phase alternators used for electrical power systems in motor vehicles. Typically, motor vehicle alternators include aluminium housings and are positioned adjacent the vehicle's engine in the engine compartment. The stator windings 12, 14, 16 are interconnected at a neutral node 18 into a wye configuration. The other end of winding 12 is connected to the anode electrode of a diode 20 and the cathode electrode of a diode 22. The other end of winding 14 is connected to the anode electrode of a diode 24 and the cathode electrode of diode 26. The other end of winding 26 is connected to the anode electrode of a diode 28 and the cathode electrode of a diode 30. The diodes 22, 26 and 30 have their anode electrodes connected to a negative output terminal 32 and are usually referred to as "negative" diodes. The diodes 20, 24 and 28 have their cathode electrodes connected to a positive output terminal 34 and are usually referred to as "positive" diodes. The negative output terminal 32 is at a lower voltage than the positive output terminal 34 and is typically connected to the alternator housing which is at ground potential. Oftentimes, a capacitor 36 is coupled between the output terminals 32 and 34 for noise suppression, for example, to prevent interference with the reception of a radio within a motor vehicle. An additional pair of diodes 38 and 40 having their cathode electrode and anode electrode, respectively, connected to the neutral node 18 of the windings, and their anode electrode and cathode electrode, connected to output terminals 32 and 34 respectively, may be included for additional current output at high operating speeds. Referring now to Figure 2, the rectifier bridge assembly 42 including an improved terminal according to the present invention, is shown for carrying the circuit 10. The bridge assembly 42 comprises a plurality of positive diodes 20, 24, 28, 40, only one of which is shown in Figure 2, with each positive diode having first, anode electrode, and an opposite, cathode electrode. A plurality of negative diodes 22, 26, 30, 38, is also included again with only one being shown in Figure 2, with each negative diode having a first, anode electrode and an opposite, cathode electrode. A plastic circuit member 47 is substantially as shown and described in U.S. Patent No. 5,043,614, incorporated herein by reference. The plastic member 47 is adapted to be secured to an end plate 44 (not shown), carries a generally crescent-shaped radiator plate 49, and first electrical circuit means comprising a plurality of conductor members embedded therein and electrically insulated from one another by the plastic of the plastic circuit member 47. Embedded conductors effecting the connections shown in Figure 1 are generally designated at 88. The radiator plate 49 has apertures 54 formed in radially extending portions 56 thereof for receiving the cathode electrodes, of the positive diodes 20, 24, 28, 40 with the anode electrodes, extending beyond the radiator plate 49. The radially extending portions 56 are generally aligned with the arms of the plastic circuit member 47. The plastic member 47 is secured to the end plate (not shown) and includes passage means comprising semicircular indentations for passing cathode electrodes of the negative diodes 22, 26, 30, 38. While a variety of devices including rivets may be used to secure the plastic circuit member 47 to the end plate, preferably the plastic circuit member 47 includes plastic extensions 57 which are extended through corresponding openings and heat staked. The radially extending portions 56 are also separated from one another by airflow means comprising louvres in the illustrated embodiment for passing cooling air through the positive radiator plate 49. The conductor member 88 connects anode/cathode electrodes of pairs of the diodes 20, 22, 24, 26, 28 to the stator windings 12, 14, 16 of the alternator after the plastic circuit member 47 is secured to the alternator housing end plate. The radiator plate 49 includes a first output of the alternator corresponding to the positive output terminal 34, and the alternator housing end plate defines a second output of the alternator corresponding to the negative output terminal 32. The radiator plate 49 defines the terminal means for making an electrical connection at the terminal 34. The end plate of the alternator forms the other terminal 32 as described in U.S. Patent No. 5,043,614. As best shown in Figure 3, the radiator plate 49 includes a connector plate 60, which has been bent for alignment perpendicular to a radially extending portion 56, and including an opening 62. The opening 62 receives the stem of a fastener such as the threaded stem 66 of the bolt 64. The bolt 64 has an enlarged head 68 with a knurled peripheral surface 70. The stem 66 is inserted through the opening 62 before the radiator plate 49 is inserted into a mould in accordance with the process discussed in U.S. Patent No. 5,043,614. The connecting plate 60 includes an axially extended portion 72 at the periphery of the opening 62 extending in the direction of the exposed stem 66. A tapered surface portion 74 lies adjacent the axially extended portion 72 to enable the plastic material flowing during the mould process to remain retracted from the contact surface 72 formed by the axially extended surface against which a terminal such as a harness eyelet may be pressed by a nut. During the moulding process, the bolt 64 may be inserted so that its head 68 is flush against the connecting plate 60 by means of the mould part 76. However, since the contact surface 72 is kept free of plastic material by the mould insert 78, the connecting plate directly engages the harness eyelet without using the bolt 64 as a conductor. The plastic body is also shaped in the mould to form an axially extending, circumferentially interrupted wall around the connecting plate 60. As shown in Figure 2, two interruptions provide a pair of walls that obstruct rotation of a harness eyelet installed over the bolt 64 as it is tightened against the contact surface 72 by a nut. As a result, it will be understood that the present invention provides a means for securely attaching directly contacting conductive terminals such as harness eyelets to the rectifier output. Such terminals may be squeezed against the contact surface between the head of the bolt 64 and a nut. Such a connection avoids limited current carrying capacity of previously known spade connectors and avoids the loosening problems associated with the plastic sleeve supporting the previously known two nut clamping arrangement. In addition, the bolt is securely positioned in a fixed orientation by the plastic body surrounding the bolt, and the plastic body insulates the bolt from electrical contact with adjacent components. Moreover, the moulded plastic joins with the knurled surface 70 on the enlarged head 68 to prevent rotation while a nut is being tightened on the stem. Furthermore, the coupling uses substantially fewer components than previously known bolt assemblies used as electrical connectors for alternators. Furthermore, the fastener need not be constructed as a conductor and a conventional bolt will not be relied upon as a conductor.

Claims: A rectifier bridge assembly for attachment to a polyphase alternator housing comprising: a generally crescent-shaped radiator plate (49), a plastics circuit support member (47) insert moulded around the radiator plate (49), a fastener (64) having a stem (66) and an enlarged head (68) ; an extended connector plate (60) formed integrally with the radiator plate (49) and having an opening (62) receiving the stem (66) of the fastener (64) and an exposed annular surface surrounding the stem (66) for making direct contact with a connection terminal which in use is clamped against the exposed annular surface by the fastener (64), and a cavity formed in said support member (47) adjacent said opening (62) receiving the enlarged head (68) of the fastener (64). An assembly as claimed in claim 1, wherein said radiator plate (49) is made by stamping. An assembly as claimed in claim 1 or 2, wherein said connector plate (60) includes an axially raised surface (72) at the periphery of the opening (62). An assembly as claimed in claim 3, wherein said connector plate (60) includes a tapered surface (74) extending radially outwardly from said raised surface (72). An assembly as claimed in any preceding claim, wherein said support member (47) includes a circumferentially interrupted, peripheral wall around the connector plate (60) and extending axially from said connector plate (64). An assembly as claimed in any preceding claim, wherein said support member (47) includes a plurality of conductor members (88) embedded therein and electrically insulated from one another thereby; said radiator plate has a plurality of apertures (54) formed in radially extending portions (56) thereof for receiving a like plurality of diodes (20,24,28) ; said plurality of diodes each having a first electrode and an opposite second electrode, apertures in a portion of the housing receiving like electrodes and said apertures (54) of said radiator plate (49) all receiving like opposite electrodes; and further including means (57) for securing said member (47) to said housing; said conductor members (88) connecting electrodes of pairs of said diodes associated with stator windings (12,14,16) of the alternator after securing said member (47) to said alternator housing, wherein said radiator plate (49) defining a first output (34) of said alternator and said alternator housing providing a second output (32) of said alternator, and wherein said first output comprises said connecting plate (60) carrying the fastener (64).

Inventors: YOCKEY STEVEN J, YOCKEY, STEVEN J.
Applicants: FORD MOTOR CO, FORD MOTOR COMPANY
Application year: 1993
Main classification: H02K5
IPC codes: H02K19, H02K5, H02K11