Metal deforming – By use of tool acting during relative rotation between tool... – During rotation of work
Patent
1999-01-26
2000-12-19
Larson, Lowell A.
Metal deforming
By use of tool acting during relative rotation between tool...
During rotation of work
2989332, B21H 500
Patent
active
061614092
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method of producing an externally toothed gear part from a metallic workpiece that is in the form of a blank or a predrawn part. The gear part so produced has a hub face with teeth projecting outward therefrom. The invention also relates to an apparatus for producing an externally toothed gear part having a hub face with teeth projecting outward therefrom.
Externally toothed gears are used on a large scale, for example, as flywheels for shift transmissions or starters in motor vehicle construction. Such gear parts were hitherto produced by the flywheels, for example, being designed in two pieces. In this case, the flywheel disk was produced from cold-worked plate and the external tooth system was formed in a separate ring by means of a chip-producing forming method. The ring was then welded to the flywheel disk. This known arrangement has the disadvantage that it is costly and that material changes, which cannot be fully ascertained, are induced in the flywheel by the welding process.
In order to reduce the total weight of a gear part, while retaining sufficient strength, in both the disk region and the region of the external tooth system, it has already been proposed in EP-0 333 917 A2 that the external tooth system be formed from a marginal region of the plate blank, the marginal region being thickened relative to the latter before the external tooth system is formed, in such a way that the cross section of the external tooth system is larger than the cross section of a correspondingly long ring zone having the plate thickness of the plate blank.
To this end, before the forming of the external tooth system, the relevant marginal region is thickened by means of suitable sheet-metal working processes; such as upsetting or the like, as a result of which structural changes are induced in the material. Since carbon steel is normally used for these gear parts, hardening, which is disadvantageous for the subsequent working process, inevitably occurs. In this embodiment, the teeth are then formed by hammering them in according to a method which likewise belongs to the prior art. Furthermore, this second-mentioned procedure has the disadvantage that the tooth flanks may repeatedly turn out to have inadequate load-bearing capacity, so that the teeth may break under high loads. In addition, the known arrangement has the disadvantage that the teeth are not only formed on the outside of the marginal region of the blank; on the contrary, a tooth-like undulation of this marginal region is also made at the rear toward the interior of the blank, so that quite considerable generation of noise occurs as a result during rotation of the wheel.
EP-0 140 576 A1 has disclosed a flywheel which is produced from a pressed part, i.e. a predrawn part, in which case teeth provided on the outside of an axially extending section are produced by rolling. The drawing shows this component as if the inner ring of the teeth is of smooth design. This method has the disadvantage that a predrawn part is taken as a basis, the wall thickness of the axially extending cylindrical region corresponding exactly to the wall thickness of the hub face, so that either the root rim of the toothed ring is too thin and too weak, so that the teeth may break, or else the hub face is too thick, so that here material is wasted and an undesirable increase in weight occurs.
DE-40 06 582 A1 discloses a method of producing a gear wheel, in which method the toothed roller rotates about an axis which is disposed in the circumferential direction of the workpiece to be worked, and in which the metal-forming work is split up into a multiplicity of individual metal-forming steps, i.e. the teeth are hammered into the margin of the workpiece, so that destruction of the structure occurs, i.e. the grain flow of the metal is destroyed and fractures may subsequently occur here.
In the procedure according to DE-39 32 823 C1, the teeth are also pressed into an axial surface, the thickness of which corresponds to the wall thickness of the hub face.
U.S.
REFERENCES:
patent: 3261192 (1966-07-01), Saito et al.
patent: 4273547 (1981-06-01), Bytzek
patent: 4485656 (1984-12-01), Nilson et al.
patent: 5562785 (1996-10-01), Yamanaka
Larson Lowell A.
WF-Maschinebau und Blechformtechnik GmbH & Co. Kommanditgessells
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