This invention relates to an Lundell type alternator rotor claw and a method of manufacturing the same. The alternator is usually, though not exclusively, intended for use on automobiles such as passenger cars, utility vehicles, and commercial vehicles.

The Lundell type rotor claw pole is crucial to the enhancement of power output of an alternator. The fingers of the claw pole play a vital role in connection with both output and noise level of an alternator.

At present such claws are manufactured by one of the following methods:

Forming from sheet metal:

The claw blank is stamped out of sheet metal and subsequently bent out of the plane of stamping and formed in 3 or 4 stages. The core or the hub is made from solid bar material.

Hot forging:

Slug is sheared from hot rolled bar, heated to 1200°C above the critical temperature, and formed in number of stages, and flashes trimmed, and machined to achieve required part accuracy.

Cold Extrusion:

Slug is sheared from rolled bar, cold extruded in several stages with high tonnage presses and with intermediate chemical treatments.

Warm forging:

In this process, the raw material in the form of slug sheared from bar stock, is induction heated to a temperature between 680°C and 800°C and warm formed to achieve the part geometry, followed by phosphating and cold sizing providing the exact final dimensions.

The results of all the above methods have the following disadvantages.

Forming from sheet metal, no doubt achieves an adequate production rate but the material scrap rate is high, finger geometry not accurate, and the magnetic properties are impaired because of the core which is produced as a separate piece, resulting in noise.

Hot forged pole pieces show improved quality; however this method results in low production rates and high energy consumption, heavy material loss due to subsequent machining and high cost of production with low tool life.

The cold extrusion process is expensive with high tonnage/power equipments and because of required intermediate chemical treatments, and additional part transport and storage capacities. Viable only when volumes are very high.

Warm forging process though is more economical compared to the above processes with the existing slug route, the material savings and cost savings can be further improved with the present invention.

It is therefore an object of the present invention to achieve material and cost savings and at the same time accuracy.

The accompanying drawings illustrate in

Fig. 1 the known construction 1 of a rotor claw and the two-part construction of the rotor claw according to this invention, consisting of parts 1.1 and 1.2

Fig. 2 the method of manufacture according to the known art

Fig.3 the method of manufacture of the rotor claw according to this invention

In Fig. 1, Part 1 is the known claw. Part 1.1 and Part 1.2 are parts of the proposed claw.

The proposed claw consists of a warm forged ring 1.1 produced from a rack, rolled and welded. The warm forged ring will have a precise finger profile and is bore machined.

The proposed claw also consists of a cold forged or warm forged core 1.2 machined to predetermined dimensions.

The warm forged ring and cold forged / warm forged machined core are fitted together by means such as shrink fitting or press fitting to form a rigid connection and, thereafter, cold sized to provide exact final dimensions.

In Fig. 2 illustrating the known art, the Input raw material in the form of slug, is indicated by 2-10, the dimensions of which will account for the final volume of the product and the design scrap generated after undergoing the various stages of the process.

2-11: Is the input raw material slug induction heated and graphite coated.
2-12: Is the upset slug from the induction heated slug at 2-11.
2-13: Is the preliminary forged claw from the upset slug at 2-12.
2-14: Is the final forged claw from the pre formed forged claw at 2-13.
2-15: Is the trimmed claw from the forged claw at 2-14.
2-16: Is the annealed claw from the trimmed claw at 2-15.
2-17: Is the shot blasted claw from the annealed claw at 2-16.
2-18: Is the phosphated claw from the shot blasted claw at 2-17.
2-19: Is the cold coined claw from the phosphated claw at 2-18.
2-20: Is the precision trimmed claw from the cold coined claw at
2-19. 2-21: Is the washed claw from the precision trimmed claw at 2-20. 2-22: OD and face turned claw from the precision trimmed claw at 2-21. 2-23: Hole drilled and half core faced claw from the OD and faced claw at 2-22.

In Fig. 3 the input raw material in the form of a strip is indicated by 3-30, the dimensions of which will account for the final volume of the product and the design scrap generated after undergoing the various stages of the process.

3-31: Is a plain strip or a strip notched with a preform profile for finger extrusion, from the input strip material at 3-30 3-32: Is rolled ring from the notched strip at 3-31. 3-33: Is a welded ring from the rolled ring at 3-32. 3-34: Is a machined welded ring from the welded ring at 3-33. 3-35: Is a warm forged ring at 680°C and 800°C from the machined welded ring at 3-34. 3-36: Is an annealed warm forged ring from the warm forged ring at

3-35. 3-37: Is a machined warm forged ring from the annealed warm forged at 3-36. 3-38: Is the Input material in the form of a slug, the dimension of which will account for the final volume of the core. 3-39: Is the extruded preformed core from the input material at 3-38. 3-40: Is the finished cold forged core from the pre extruded core at

3-39. 3-41: Is the machined cold forged core from the cold forged core at

3-40. 3-42: Is the shrink fitted assembly from the Input material at the 3-37 and at 3-41. 3-43: Is the two hole drilled assembly from the Input assembly 3-42. 3-44: Is the sized assembly from the input assembly at 3-43.

It will be appreciated from the foregoing description that various other embodiments of this invention are possible without departing from the scope and ambit thereof.

We Claim:

1. A Lundell type alternator rotor claw comprising a first unit of a warm forged ring fitted with a second unit of a cold forged / warm forged and sized core, by means including shrink fitting or press fitting, the said units together to form an integral, rigid assembly, the ring consisting of a rack, rolled, welded, cold forged / warm forged and machined to form the said first unit, while the said core consists of a cold forged / warm forged and machined second unit of predetermined size, the assembly being finally cold sized.

2. A Lundell type alternator rotor claw substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

3. A method of manufacture of a Lundell type alternator claw comprising the steps of rolling, welding, cold forging / warm forging and machining a rack to obtain a warm forged ring; cold forging / warm forging and machining a core to predetermined size; the assembly of the said claw being carried out by means including shrink fitting or press fitting the said ring with the said core, to obtain an integral rigid connection; and finally cold sizing the assembly.