Method for modifying the flanks of a gear wheel tooth with the aid of a tool

Abstract

The invention relates to a method for modifying the geometry of gear wheel tooth flanks with a tool with a toothing that engages with the gear wheel during a precision machining. A varied profile is produced on the tool over the width of the tool, in that during a dressing procedure a dressing wheel is moved along the tooth flank of the tooth to be dressed. The width of the teeth of the dressing wheel is much smaller than the width of the tool. In order to cover the width of the tool a length must be covered corresponding to a multiple of the width of the teeth of the dressing wheel. After the dressing, the precision machining of the gear wheel is carried out with the tool. Since the dressing wheel is moved with a changing pitch and a changing crossed axes angle relative to the tool, the modification of the tooth flank geometry can be reproduced in the tool. A modification of the crossed axes angle dependent on the helical angle of the tool takes place with equalization of the helical angle of the tool changing over the width of the teeth of the tool.

Claims

1. A method for modifying a geometry of tooth flanks of a gear wheel with the aid of a tool, which has a toothing engaging with the teeth of the gear wheel during a precision machining, wherein the following working steps are performed: a) forming a profile on the tool varying over a width of the tool, in which a dressing wheel is moved during a dressing procedure along the tooth flank of the tooth to be respectively dressed, wherein the width of the teeth of the dressing wheel engaging with the tool to be dressed is smaller than the width of the tool to be dressed to such an extent that, in order to cover the width of the tool to be dressed, the dressing wheel has to be moved by a length in a direction that corresponds to a multiple of the width of the teeth of the dressing wheel, and b) precision machining of the gear wheel with the tool that has been dressed in this way, wherein the dressing wheel during the working step a) is moved with a changing pitch and a changing crossed axes angle in relation to the tool to be dressed, in order to incorporate the respective modification of the tooth flank geometry into the tool, and wherein the precision machining of the tooth in the working step b) takes place in the machining process by a modification of the crossed axes angle dependent on the helical angle of the tool with equalization of the changing helical angle of the tool over the width of the teeth of the tool.

2. The method according to claim 1, wherein during the dressing the narrow dressing wheel and the tool to be dressed are rotatably driven respectively about a rotation axis via respectively their own individually controllable drive.

3. The method according to claim 2, wherein individually controllable servo-drives are provided for adjusting the relative position of the tool to be dressed and the dressing wheel in the direction of the rotation axis of the dressing wheel as well as a direction aligned transverse thereto.

4. The method according to claim 1, wherein an individually controllable servo-drive for swivelling the dressing wheel or the tool to be dressed can be swivelled about an axis radially aligned in relation to the tool to be dressed.

5. The method according to claim 1, wherein an individually controllable servo-drive is provided for adjusting the relative position in a direction radially aligned in relation to the tool to be dressed.

6. The method according to claim 1, wherein the width of the teeth of the dressing wheel engaging with the tool to be dressed corresponds at most to a fifth of the width of the tool to be dressed.

7. The method according to claim 6, wherein the width of the teeth of the dressing wheel engaging with the tool to be dressed corresponds at most to an eighth of the width of the tool to be dressed.

8. The method according to claim 1, wherein in the dressing the tooth of the dressing wheel respectively engaging with the tool to be dressed contacts in a punctiform manner the tool to be dressed in at least one of its edge regions.

9. The method according to claim 1, wherein in the dressing the tooth of the dressing wheel respectively engaging with the tool to be dressed contacts in a linear manner the tool to be dressed in at least one of its edge regions.

10. The method according to claim 7, wherein in the dressing the tooth of the dressing wheel respectively engaging with the tool to be dressed contacts in a linear manner the tool to be dressed in at least one of its edge regions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in more detail hereinafter with the aid of exemplary embodiments and drawings, which respectively show diagrammatically:

(2) FIG. 1 a device for dressing a tool for the honing machining of an externally toothed gear wheel;

(3) FIG. 2 the device according to FIG. 1 in a side view;

(4) FIG. 3 a section of the dressing wheel engaging with the tool, from above;

(5) FIG. 4 a dressing wheel used in the device according to FIG. 1, in a perspective representation;

(6) FIG. 5 the device according to FIG. 1 in the precision machining of the externally toothed gear wheel.

DETAILED DESCRIPTION OF THE INVENTION

(7) The tool 1 illustrated in FIG. 1 is intended for honing the toothing of an externally helical toothed gear wheel Z. For this purpose it is of annular shape and has an internal helical toothing 2.

(8) A dressing wheel 3 is provided for dressing the tool 1.

(9) The width B.sub.A of the dressing wheel 3 is typically less than one eighth of the width B.sub.W of the tool 1 to be dressed. Correspondingly the length L by which the dressing wheel 3 has to be moved in the direction of its rotation axis C (movement axis Z or Z direction) in order to cover the width B.sub.W of the tool 1 is more than eight times the width B.sub.A of the dressing wheel 3.

(10) Neither the spatial allocation nor the width ratios are shown correctly to scale in the figures.

(11) To adjust the dressing wheel in the Z direction and the X direction (movement axis X) aligned transverse thereto relative to the tool 1 to be dressed, individually controllable adjustment devices are provided (not shown here), as are normally present on conventional machines of this type. In addition the pitch of the turns completed by the tool 1 to be dressed and by the dressing wheel 3 about the B and/or C axes can be changed. This can be effected by means of the mutually independent drives that are provided for rotating the dressing wheel 3 and tool 1 to be dressed about the respectively associated rotation axis C and B.

(12) During the dressing operation the rotation axis C of the dressing wheel 3 is at a crossed axes angle Z to the rotation axis B of the tool 1 to be dressed. In order to be able to vary the crossed axes angle Σ during the movement of the dressing wheel 3 along the tooth flank 5 to be respectively dressed, the dressing wheel 3 and the tool 1 can be swivelled relative to one another by means of a further individually controlled servo-drive about a pivot axis Y that is radially outwardly aligned in relation to the tool 1 to be dressed, on the plane defined by the Z and X movement axes.

(13) The adjustment devices responsible for the movement in the X and Z directions as well as the drives for the rotations about the B, C and Y axes are controlled via a programmable machine control, also not shown here.

(14) The flanks 5 of the teeth 6 of the dressed tool 1 are aligned at a helical angle β inclined to the rotation axis B of the tool 1.

(15) The respective greatest diagonal D of the narrow teeth 16 of the dressing wheel 3, which in cross-section are formed orthogonally in their basic shape, corresponds substantially to the respective normal distance A.sub.n of the flanks 5 of the teeth 6 of the tool 1 to be dressed. In this way the tooth 16 of the dressing wheel 3 that is respectively in engagement contacts the mutually associated flanks 5 of the adjacently arranged teeth 6 of the tool 1 to be dressed, in each case only in a punctiform manner with its diagonally opposite edges 8, 9.

(16) In order to execute this machining under the aforementioned adjustments, the gear wheel ZR to be respectively processed is placed at the position of the dressing wheel 3 in the respective device and a honing machining is performed on the gear wheel Z by means of the tool 1 dressed in the afore-described manner under the also afore-discussed adjustments and machining conditions. In this connection the flank modification previously carried out by means of the dressing wheel 3 on the honing tool 1 is transferred to the gear wheel ZR. In this way the tooth flanks 17, 18 of the teeth 19 of the gear wheel ZR after completion of the honing machining performed by the tool 1 exhibit the relevant modification, although they are not present on the dressing wheel 3 used according to the invention, but according to the invention had been produced simply by changes of the relative position on the hard-fine machining tool 1 performed about the axes X, Y, Z and B, C by means of the machine control.

(17) In the method according to the invention for modifying the geometry of tooth flanks of a gear wheel ZR with the aid of a tool 1, which has a toothing that engages with the gear wheel ZR during the precision machining, a varied profile is thus produced over the width B.sub.W of the tool 1, in that during a dressing procedure a dressing wheel 3 is moved along the tooth flank 5 of the tooth 6 to be dressed. The width of the teeth 16 of the dressing wheel 3 is in this connection much smaller than the width B.sub.W of the tool 1. Therefore the dressing wheel 3 must be moved by a length L corresponding to a multiple of the width B.sub.A of the teeth 16 of the dressing wheel 3 in order to cover the width B.sub.W of the tool 1. After the dressing the precision machining of the gear wheel ZR is carried out with the tool 1. Since in this connection the dressing wheel 3 is moved with a changing pitch and a changing crossed axes angle Σ referred to the tool 1, the modification of the tooth flank geometry can be reproduced in the tool 1. In the subsequent precision machining a modification of the crossed axes angle Σ dependent on the helical angle of the tool 1 takes place in the machining process with equalization of the changing helix angle of the tool 1 over the width of the teeth 16 of the tool.

REFERENCE NUMERALS

(18) 1 Annular tool for honing the toothing of an externally helically toothed gear wheel 2 Internal helical toothing of the tool 1 3 Dressing wheel 4 Carrier of the dressing wheel 3 5 Tooth flanks of the teeth 6 6 Teeth of the tool 1 to be dressed 7 Tooth flanks of the dressing wheel 3 8, 9 Edges in the region of the transition between the tooth flanks 7 and the front surfaces 11, 12 of the dressing wheel 3 11, 12 Front surfaces of the dressing wheel 3 13, 14 Curved sections 15 Surface section 16 Teeth of the dressing wheel 3 A.sub.n Normal distance of the flanks 5 β Helical angle B Rotation axis of the tool 1 β* Angle B.sub.A Width of the dressing wheel 3 B.sub.W Width of the tool 1 to be dressed C Rotation axis of the dressing wheel 3 Diagonal L Length by which the dressing wheel 3 has to be moved in the direction of its rotation axis C (Z direction) in order to cover the width B.sub.W of the tool 1 m.sub.n Normal module m.sub.t Transverse module of the tool 1 to be dressed Σ Crossed axes angle Y, X, Z Movement axes ZR Gear wheel