METHOD FOR GEAR SHAPING A TOOTHING, CONTROL PROGRAM, AND GEAR SHAPING MACHINE FOR CARRYING OUT THE METHOD

Abstract

The invention relates to a method for gear shaping a toothing (55) with a specified normal pitch (m.sub.n), angle of action (?), and optionally a helix angle (?) on a workpiece (50), wherein a shaper cutter (40) moving in stroke cycles with a specified stroke length (h) removes material from the workpiece in multiple working strokes in a rolling machining engagement, thereby forming contact tracks, wherein the contact track on the partial circle in the stroke center runs at an angle (?) to the flank line (57) at least for a first plurality of strokes, the cotangent of said angle being smaller than or equal to the product of a constant of 40, preferably 33, in particular 25, and a geometry/process factor.

Claims

1. Method for gear shaping a toothing with a specified normal pitch (m.sub.n), angle of action (?), and a helix angle (?) on a workpiece, wherein a shaper cutter moving in stroke cycles with a specified stroke length (h) removes material from the workpiece in multiple working strokes in a rolling machining engagement, thereby forming contact tracks, characterized in that the contact track on the partial circle in the stroke center runs at an angle ? to the flank line at least for a first plurality of strokes, the cotangent of said angle being smaller than or equal to the product of constants K.sub.1 and K.sub.2, wherein K.sub.1 is in the range of 19.4 to 40, and K.sub.2 is a geometry/process factor of K.sub.2=K.sub.h.Math.K.sub.m.Math.K.sub.?.Math.K.sub.? with K.sub.h=h [mm]/20, K.sub.m=3/m.sub.n [mm], K.sub.?=sin 20?/sin ? and K.sub.?=cos ?.

2. Method according to claim 1, wherein the shaper cutter is fed via the first plurality of strokes and a feed parameter defined by the quotient of radial feeding per workpiece revolution and the lifting amount of the shaper cutter between working stroke and return stroke in the first plurality of strokes is less than 1.4.

3. Method according to claim 2, wherein the feed parameter is less than 1.3.

4. Method according to claim 1 wherein the first plurality of strokes takes place over a feed region with a predominant share of the overall feed for completion of the shaped toothing, and the cotangent ? is greater than 40.Math.K.sub.2 over a subsequent further feed region.

5. Method according to claim 1 wherein during a last feeding to final feed depth of the shaped toothing the cotangent ? is greater than 80.Math.K.sub.2.

6. Method according to claim 1 wherein the toothing is a straight toothing or the helix angle of the toothing is less than 14?.

7. Method according to claim 1 wherein the tooth width is at least 60% of the stroke length.

8. Method according to claim 1 wherein the rolling positions differ in a shaped gap between two successive workpiece rotations in each case.

9. Method according to claim 1 wherein the stroke number is at least 30 double strokes/min.

10. Method according to claim 1 wherein the tooth width is greater than 15 mm.

11. Method according to claim 1 wherein, at least for a first plurality of strokes, a coherent contact track extends over a region of at least 20% of the full profile height of the end geometry of the shaped toothing, as viewed in the profile direction.

12. Control program which, when executed on a controller of a gear shaping machine, controls the machine to carry out a method according to claim 1.

13. Gear shaping machine comprising a controller equipped with a control program according to claim 12.

14. The method of claim 2 wherein the shaper cutter is fed via the first plurality of strokes in a constant spiral feed.

Description

[0021] Further features, details and advantages of the invention will be apparent from the following description with reference to the accompanying figures, of which

[0022] FIG. 1 shows a schematic diagram for the machining engagement during gear shaping,

[0023] FIG. 2 shows an angle between contact track and flank line on the partial circle in the stroke center, and

[0024] FIG. 3 shows a qualitative comparison of contact tracks as compared to the prior art.

[0025] It can be seen in FIG. 1 how a shaper cutter 40 comes into machining engagement with a workpiece 50 in order to shape a toothing 55 thereon. Shown is the situation during the working stroke at the beginning of the engagement, from which the shaper cutter 40 is moved downwards along the stroke axis Z, while the shaper cutter 40 and the workpiece 50 are in meshing engagement with one another, for which purpose the rotational speeds of the skiving wheel 40 and the workpiece 50 are synchronized in a known manner. In this exemplary embodiment, the stroke movement is carried out with a crank drive as in the prior art; in the given exemplary embodiment, a stroke length of approximately 20 mm is set, with a stroke number of 500 double strokes (working stroke+return stroke) per minute and a rolling speed of 0.95 strokes per division, in order, for example, to shape a straight teething on workpieces. It is understood, however, that the invention is not limited to specific toothing types, such as external toothings or internal toothings; internal toothings are preferably shaped as well. It is also understood that the invention is not limited to specific toothing widths, correlating stroke lengths or pitch sizes; in the present exemplary embodiment, the pitch (normal pitch) of the toothing is, for example, 3 mm and the toothing is a straight toothing. However, the invention can also be applied to helical toothings, but the helical toothing should preferably be less than 14? or the values indicated above.

[0026] As regards the design of a suitable gear shaping machine, the designs already known from the prior art can be used, for example the design shown in DE 10 2019 004 299 A1, in which the lifting movement for the return stroke is effected by a rotationally driven cam with a predetermined profile. Said document is incorporated herein by reference in respect of an exemplary design of a toothing machine.

[0027] In FIG. 2 (for explanatory or definition purposes; obviously, the form of the gear shown in FIG. 2 differs from that of FIG. 1), the angle ? (in the stroke center, which in this exemplary embodiment coincides with the center with respect to the width direction of the toothing 55) is drawn between a contact track of the shaping operation and the flank line 57 on the partial circle on a tooth flank 56. This angle is extremely narrow even in the case of conventional gear shaping with a spiral-degressive feed (as indicated by reference sign 58 in FIG. 1, typical machining tracks run almost parallel to the flank line during conventional gear shaping). In the configuration according to the invention, this angle is considerably larger and its cotangent is considerably smaller, respectively; in the exemplary embodiment in which the second factor K.sub.2 is 1 for reasons of simplicity and does not provide any corrections, a value of about 20 being reached for the cotangent ?.

[0028] In FIG. 3, the difference between an exemplary embodiment of the invention (FIG. 3A) and the prior art (FIG. 3B) is juxtaposed once again in a pure relative representation without observing the absolute values (shown in an excessively distorted manner); one can see the machining tracks which extend in a clearly more oblique manner over the tooth flanks 56, which machining tracksdespite no lower stroke numbersresult in both good machining qualities of the shaped toothing 55 and a material removal with lower tool wear.

[0029] It is understood that the invention is not limited to the detail features shown in the exemplary embodiments. Rather, the individual features of the above description and of the claims below may be essential, individually and in combination, to the implementation of the invention in its various embodiments.