1. Technical Field
This invention relates to the field of heavy duty alternators and, more particularly, to an improved stator terminal insulator and parts kit for use in the manufacturing and remanufacturing of oil-cooled 50 DN alternators that produce a direct current (DC) output for use in conjunction with bus or coach vehicle electrical systems.
2. Discussion of the Related Art
The use of a totally enclosed oil-cooled 50 DN alternator that includes a three-phase stator winding assembly with three phase leads and associated terminals is generally known in the art. More specifically, an oil-cooled 50 DN alternator is a brush-less alternator with a stationary field winding assembly, a stationary stator winding assembly, and a rotating rotor that is cooled by a continuous flow of oil supplied by an associated internal combustion engine. The stator windings are enclosed in an aluminum case and are electrically coupled to six diodes that form a rectifier. A rectifier end frame housing assembly contains the rectifier and is connected to a top end of the stator case from which the stator terminals extend. A bottom end of the stator case is connected to a drive end frame assembly that contains a ball bearing, a roller bearing, a collar, and oil seal assembly. The bearings, collar and oil seal assembly are press fit on the rotor such that the rotor rotates between the stator winding assembly and the field winding assembly creating electrical currents. The rectifier end frame assembly, the stator assembly, and the drive end frame assembly are assembled with insulators and o-rings forming an oil-proof assembly for the circulating cooling oil. By way of example, additional features and specifications of a typical belt driven oil-cooled 50 DN alternator (generator) that are well know to one skilled in the art are described in Delco Remy Service Bulletin 1G-258 dated Sep. 1, 1986.
Transit bus and coach vehicle applications commonly utilize oil-cooled 50 DN alternators to produce a direct current (DC) output to meet the electrical demands of these vehicles. Unfortunately, due to increasing electrical demands on transit buses and coaches, oil-cooled 50 DN alternators are subjected to increasing operating temperatures, electrical loads and engine vibration that shorten the life cycle of these alternators. A common fault mode is when a stator assembly fails due to a mechanical or insulation failure in the winding assembly resulting from the increasing demand that an alternator is subjected to. It is common practice that once an oil-cooled 50 DN alternator fails, the alternator is remanufactured to its original specifications. This is accomplished by disassembling all or a portion of the alternator's components and by replacing a defective stator assembly with a new or remanufactured stator assembly along with any other failed components.
FIG. 1 shows a prior art oil-cooled 50 DN alternator stator assembly 10 that includes a steel lamination 12 with silver soldered or welded copper hair-pins 14 that form a three phase stator winding assembly 16. The three phase winding assembly 16 includes three leads 18 each with an associated brass terminal 20 for carrying the electrical current from the hair-pins 14 to a rectifier (not shown). The steel lamination 12 and the hair-pins 14 are enclosed by an aluminum stator case 22. The lamination 12 is positioned within the stator case 22 by three locking bolts (not shown) that are installed through the case 22 and into the lamination 12. The three lead terminals 20 extend a predetermined distance above a top end of the stator case 22. As will be discussed below, the three terminals 20 are positioned such that they extend through three openings in a rectifier end frame housing during assembly of the stator assembly 10. Three planar insulators 24, Delco Remy part number 1941051, are installed over the terminals 20 about end sections 26, and the leads 18 are covered with insulated sleeving material 28 to prevent shorting with the stator case 22.
A commonly known prior art oil-cooled 50 DN alternator stator assembly includes three stator leads formed from rigid copper wire that is welded to the stator's lead terminals. This is commonly referred to a rigid lead design stator assembly. It is common to form the rigid leads as an extension of hair-pin coils that form the stator's winding assembly. Unfortunately, it is well know to one skilled in the art that the rigidity of such a stator lead design causes the stator assembly to be prone to failure wherein the leads and/or associated terminals break off from the wound hair-pin assembly. Such failures are due to the operational conditions of the alternator wherein the stator assembly is exposed to high temperatures and extreme vibrations.
As an improvement to the rigid lead design, the stator assembly 10 incorporates a flexible lead design wherein the leads 18 are formed from flexible stranded wire that is electrically connected to the hair-pins 14 and the terminals 20. As disclosed in U.S. Pat. No. 6,825,586 and in the Delco Remy publication titled “50 DN Alternator Product Improvements” dated Oct. 28, 2002, a problem associated with stator assemblies such as the stator assembly 10 of FIG. 1, referred to as the Current Design in the publication, is that the #8 AWG flexible leads 18 with the terminals 20 are difficult to assemble due to independent movements of the terminals 20.
FIG. 2 shows another prior art oil-cooled 50 DN alternator stator assembly 40. U.S. Pat. No. 6,825,586 and the above-referenced “50 DN Alternator Product Improvements” publication disclose and teach the use of a rigid one-piece stator and terminal lead insulator 60, shown in FIG. 2 as part of the stator assembly 40, as the original equipment manufacturer's (OEM) improvement to the problems associated with the Current Design stator assembly 10 of FIG. 1. The stator assembly 40 is referred to as the New Design in the above-referenced Delco Remy publication. The stator assembly 40 includes a steel lamination 42 with silver soldered or welded copper hair-pins 44 that form a three phase stator winding assembly 46. The three phase winding assembly 46 includes three #6 flexible bare cable leads 48 each with an associated terminal 50 for carrying the electrical current from the hair-pins 44 to a rectifier (not shown). Unlike the stator assembly 10, the leads 48 are not covered with any insulating material such that the outer surfaces of the leads 48 are exposed. The steel lamination 42 and the hair-pins 44 are enclosed by an aluminum stator case 52. The lamination 42 is positioned within the stator case 52 by locking bolts 54 that are installed through the case 52 and into the lamination 42. The three lead terminals 50 extend a predetermined distance above a top end of the stator case 52. The rigid one-piece stator lead and terminal insulator 60 receives and, as disclosed in the prior art, snugly holds all three of the terminals 50. Furthermore, the rigid one-piece insulator 60 is secured to the unsupported bare cable leads 48 with ties 62 such that, as disclosed in the prior art, the leads 48 are fixed to the insulator 60 along the circumference of the insulator 60. The exterior circumference of the insulator 60 is positioned just inside the interior circumference of the case 52. O-rings 64 are positioned on the terminals 50 above three cylindrical retainers 66 of the rigid one-piece insulator 60.
The rigid one-piece insulator 60 is an alleged improvement to the prior art Current Design because the cable leads 48 are fixed to the rigid one-piece insulator 60 with the ties 62 and because the rigid one-piece insulator 60 prevents the terminals 50 from moving independent of one another during and after assembly of the stator assembly 40 as part of an oil-cooled 50 DN alternator. As such, the prior art New Design teaches away from the use of independently moving flexible leads in favor of fixed leads similar in nature to the prior art rigid lead design. Additionally, the prior art discloses that the rigid one-piece insulator 60 provides a thicker insulator, retainer portions 66, as compared to original top hat insulators, Delco Remy part number 1952212, that will be described in connection with FIGS. 9-11. These top hat insulators are used in conjunction with the planar insulators 24 in FIG. 1 to insulate the terminals 20 of the Current Design by extending from within the interior of an original rectifier end frame housing into three openings leading to the stator assembly 10.
As disclosed in Delco Remy Instruction Sheet, Reference 10502989, dated Apr. 10, 2003, in order to assemble the rigid one-piece insulator 60 to a rectifier frame (housing), Delco Remy part number 10471611, the three terminal holes (openings) in the rectifier frame (housing) must be drilled out to an enlarged diameter in order to accept the retainer portions 66. As disclosed in the prior art, and the importance of which will become apparent to one skilled in the art, it is important to maintain the terminal holes (openings) center locations during drilling operations.
A problem with using the rigid one-piece insulator 60 is that the increased thickness of the retainer portions 66, when compared to the thickness of the original top hat insulators, requires that the terminal openings of an original rectifier housing must be drilled out and the enlarged openings must have centers aligned with the fixed positions of the terminals 50. As a result, another problem is that the rigid one-piece insulator 60 cannot be used in conjunction with an unmodified original rectifier housing, i.e. one that has not been drilled out. Another problem is that because the one-piece insulator 60 is rigid and the terminals 50 are snugly held in position within the retainers 66, if the terminals 50 are not properly aligned with a rectifier housing's drilled out openings or if the openings are not drilled properly with aligned centers, the terminals 50 can experience side-strain forces that can cause the rigid one-piece insulator 60 to crack leading to or causing grounding or shorting conditions within the stator assembly 40. Similarly, because the leads 48 are fixed against the rigid one-piece insulator 60 with the ties 62, the leads 48 have problems similar to the prior art rigid leads in that the leads 48 do not move independently of the terminals 50. This rigidity makes the leads 48 susceptible to breaking off from their connections to the hair-pins 44 when all of the terminals 50 and rigid one-piece insulator 60 are forced to move together as a single unit during the assembly process with a drilled out rectifier housing. Also, in contrast to the statements in the prior art, the bare leads 48 are susceptible to shorting out with the case 52 due to the leads 48 close proximity to the case 52 during such movements. Additionally, the rigid one-piece insulator 60 and the leads 48 are susceptible to such failures after assembly of the stator assembly 40 as part of a new or a remanufactured oil-cooled 50 DN alternator. Post-assembly failures occur due to terminal side-strain forces and/or exposure to high temperatures and vibrations that attempt independent movements of the snugly held terminals 50 and/or the fixed leads 48 with respect one another and/or a rectifier housing and/or the winding assembly 46.
Upon failure of a 50 DN alternator, it is generally known in the art to use a kit containing component piece parts that require replacement during the remanufacturing process of the 50 DN alternators. However, the prior art does not teach or suggest the ability of removing and replacing the rigid one-piece insulator 60 after failure. Rather, U.S. Pat. No. 6,825,586 discloses and teaches, by way of example, that the securing ties 62 are made from an epoxy impregnated fiberglass cord.
It is therefore desirable to provide an improved oil-cooled 50 DN alternator stator terminal lead insulator including an electrically insulating bushing that insulates one of multiple stator terminals from a rectifier housing and provides for independent movement of the terminal and insulator with respect to the remaining terminals of the stator in order to facilitate assembly of the stator and the rectifier housing.
More particularly, it is desirable to provide an oil-cooled 50 DN alternator parts kit having at least one removable insulator for use in electrically insulating a stator with multiple leads and terminals from a rectifier housing having multiple openings while providing for independent movement of one of the terminals with respect to the remaining terminals of the stator.
It is further desirable to provide a dual application oil-cooled 50 DN alternator parts kit including at least one insulator with an insulating bushing for insulating a stator with multiple leads and terminals from a rectifier housing having multiple openings each with an original first diameter or with multiple openings that have each been increased from the original first diameter to a second larger diameter.