Gear cutting – milling – or planing – Gear cutting – Gear tooth shape generating
Patent
1995-06-06
1998-08-11
Howell, Daniel W.
Gear cutting, milling, or planing
Gear cutting
Gear tooth shape generating
409 51, B23F 100
Patent
active
057918406
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing a conical or cup-shaped crown wheel which can mesh with a cylindrical pinion whose axis of rotation intersects or crosses the axis of rotation of the crown wheel with the inclusion of an angle .alpha. deviating from 90.degree., the crown wheel being produced, starting from a workpiece, by means of a generating process in which a tool and the workpiece rotate at a constant ratio of rotation speeds and are moved relative to each other in such a manner that the tool continuously works the workpiece.
For a proper understanding of the present invention, it is pointed out that a crown wheel which can mesh with a cylindrical pinion in a mutual position of the axes of rotation in which the angle .alpha. lies between 0.degree. and 90.degree. is referred to as a conical crown wheel, and if the angle .alpha. lies between 90.degree. and 180.degree. , it is referred to as a cup-shaped crown wheel.
A generating process for producing conical and cup-shaped crown wheels is known from U.S. Pat. No. 3,184,988. In the case of this known method the tool used is a hobbing cutter whose working profile, viewed in the direction of the axis of the cutter, is a rack profile, which is also usual in the case of tools for working involute cylindrical pinions. As a result of the hobbing cutter used, the known method produces crown wheels whose teeth are characterized by barrel-shaped tooth flanks. Crown wheels with barrel-shaped tooth flanks have the disadvantage that they can be loaded only to a limited degree, through the fact that the tooth flanks do not always come into contact over the entire tooth width with the cylindrical pinion which meshes with the crown wheel.
For the production of crown wheels, it is preferable to use a hobbing cutter of the type described in the publication WO 91/04819. However, the way in which the workpiece from which the crown wheel is produced and the tool have to be positioned and moved relative to each other for accurate production of a conical or cup-shaped crown wheel with the desired teeth is not known from the prior art.
The object of the present invention is therefore to propose measures which provide a method for producing improved conical or cup-shaped crown wheels.
This object is achieved by a method of the type mentioned in the introduction which is characterized by the characterizing part of claim 1. According to this measure, the tool is positioned relative to the workpiece in such a manner that the rotation shaft of the tool runs parallel to the surface of the part of the workpiece to be worked. This means that the tool is symmetrically loaded, and the wear on the tool is minimal. The method proposed in claim 1 can advantageously be used for producing a crown wheel which can mesh with a cylindrical pinion in the case of which the axes of rotation of the crown wheel and of the cylindrical pinion intersect each other.
The present invention also provides a method of the type mentioned in the introduction, which is characterized by the characterizing part of claim 2. This method is particularly advantageous for the production of a crown wheel which can mesh with a cylindrical pinion in the case of which the axes of rotation of the crown wheel and of the cylindrical pinion cross each other. This situation is generally known as "off-centre". The method according to claim 2 is simple to carry out and leads to accurate results. The symmetrical loading of the tool is not achieved for all points of the tooth width of the crown wheel, but on average uniform wear still occurs.
The measure according to claim 3 describes the way in which the desired positioning of the tool can be achieved on a universal gear hobbing machine, while the feed motion of the tool is described in claim 4.
Claims 5, 6 and 7 describe the exact values of the envisaged settings.
The method according to the present invention will be explained in greater detail below with reference to the drawing, in which:
FIG. 1 shows a diagrammatic representation from above of the movement
REFERENCES:
patent: 1140610 (1915-05-01), Reinecker
patent: 2669904 (1954-02-01), Bloomfield
patent: 3184988 (1965-05-01), Osplack
patent: 4587766 (1986-05-01), Miyatake et al.
patent: 4650378 (1987-03-01), Zubler
Japanese Abstract--Fanuc, K.K. and Takaomi Fukuyama, Helical Crowning Control Method in Gear Hobbing Machine--No. 60-80520--Aug. 5, 1985 (Patent Abstracts of Japan, vol. 9, No. 223 (M-411) (1946).
Dr. G. Sulzer, Economics of CNC Gear Hobbing--Gear Technology (1987) Mar./Apr., No. 2, pp. 42-46.
George Sanborn, Ben Bloomfield, Effect of Axis Angle on Tapered Gear Design--Product Engineering--Feb. 1950, pp. 129-132.
Crown Gear B.V.
Howell Daniel W.
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