METHOD FOR GRINDING OF BEVEL GEARS

Abstract

A method includes the following method steps: grinding of bevel gears, wherein the respective bevel gears have a straight toothing to be ground, wherein the grinding is carried out by a disk-shaped grinding tool by discontinuous generating grinding using a predetermined rolling ratio. A cutting face of the grinding tool, which rolls during the grinding with teeth of the straight toothing of a respective bevel gear, forms a section of a hollow cone inner surface, and wherein a respective longitudinal crowning is generated on the respective straight toothing of the respective bevel gears by the grinding using the cutting face forming the section of the hollow cone inner surface. The method is distinguished in that the grinding tool is a dressable grinding tool and dressing of the grinding tool is carried out.

Claims

1. A method having the following steps: grinding of bevel gears, wherein the respective bevel gears have a straight toothing to be ground, wherein the grinding is carried out with a disk-shaped grinding tool by discontinuous generating grinding using a predetermined rolling ratio, wherein a grinding face of the grinding tool, which rolls during the grinding with teeth of the straight toothing of a respective bevel gear, forms a section of a hollow cone inner surface, and wherein a respective longitudinal crowning is generated on the respective straight toothing of the respective bevel gears by the grinding using the cutting face forming the section of the hollow cone inner surface, wherein the grinding tool is a dressable grinding tool and dressing of the grinding tool is carried out, wherein at least one first bevel gear of the bevel gears is ground before the dressing by the dressable grinding tool and wherein at least one second bevel gear of the bevel gears is ground after the dressing by the dressable grinding tool, wherein during the dressing of the dressable grinding tool, a radius of the grinding tool is reduced by the dressing from a first radius (r.sub.01) to a second radius (r.sub.02), wherein the cutting face of the grinding tool forming the section of the hollow cone inner surface is inclined before the dressing by a first hollow cone angle (γ.sub.1) and is inclined after the dressing by a second hollow cone angle (γ.sub.2), wherein a radius of curvature (r.sub.kr) of the longitudinal crowning is constant before and after the dressing, and wherein the following applies:
γ.sub.2=arcsin(r.sub.02/r.sub.01.Math.sin γ.sub.1); with r.sub.01 as the first radius of the grinding tool, with r.sub.02 as the second radius of the grinding tool, with γ.sub.1 as the first hollow cone angle, and with γ.sub.2 as the second hollow cone angle.

2. The method according to claim 1, wherein the absolute value (L) of a longitudinal crowning of the straight toothing of the first bevel gear generated by the grinding corresponds to the absolute value (L) of a longitudinal crowning of the straight toothing of the second bevel gear generated by the grinding.

3. The method according to claim 1, wherein a radius of curvature in a gap base of the straight toothing of the first bevel gear is greater than a radius of curvature in a gap base of the straight toothing of the second bevel gear.

4. The method according to claim 1, wherein the shape of the longitudinal crowning of the first bevel gear deviates from the shape of the longitudinal crowning of the second bevel gear.

5. The method according to claim 1, wherein a tool flank angle (α.sub.1, α.sub.2) of the grinding tool is adapted by the dressing and/or after the dressing, the predetermined rolling ratio between the grinding tool and the second bevel gear is adapted, wherein before and after the dressing, the same engagement angle is generated on the first and second bevel gear.

6. The method according to claim 1, wherein a tool flank angle (α.sub.1, α.sub.2) of the grinding tool is adapted by the dressing by the difference of the first angle of inclination (γ.sub.1) to the second angle of inclination (γ.sub.2), wherein before and after the dressing, the same engagement angle is generated on the first and second bevel gear.

7. The method according to claim 1, wherein right flanks of the respective straight toothing of a respective bevel gear are machined in a first infeed using first machine settings, and left flanks of the respective straight toothing of a respective bevel gear are machined in a second infeed using second machine settings.

8. The method according to claim 1, wherein no relative stroke movement takes place between the bevel gear and the grinding tool along a tooth width.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The disclosure is described in more detail hereinafter on the basis of a drawing illustrating exemplary embodiments. In the respective schematic figures:

[0029] FIG. 1A shows a tooth of a straight toothing and a grinding tool without inner hollow cone;

[0030] FIG. 1B shows the generation of a linear flank line without longitudinal crowning on the tooth according to FIG. 1A using the grinding tool according to FIG. 1A;

[0031] FIG. 2A shows a tooth of a straight toothing and a grinding tool with inner hollow cone;

[0032] FIG. 2B shows the generation of a flank line with longitudinal crowning on the tooth according to FIG. 2A using the grinding tool according to FIG. 2A;

[0033] FIG. 3 shows a straight-toothed bevel gear in a sectional illustration with a detail of a disk-shaped grinding tool;

[0034] FIG. 4 shows the bevel gear and the grinding tool from FIG. 3 in a further sectional illustration;

[0035] FIG. 5 shows a longitudinal crowning of a tooth;

[0036] FIG. 6 shows the arrangement from FIG. 4 with indicated hollow cone angle and radius of curvature of the longitudinal crowning;

[0037] FIG. 7 shows the ratio of the tool radius to the hollow cone angle at predetermined radius of curvature of the longitudinal crowning;

[0038] FIG. 8 shows a first bevel gear and the grinding tool before dressing of the grinding tool;

[0039] FIG. 9 shows a second bevel gear and the grinding tool after dressing of the grinding tool;

[0040] FIG. 10 shows longitudinal crownings before the dressing and after the dressing; and

[0041] FIG. 11 shows a flow chart of the method according to the disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

[0042] For better comprehensibility of the following explanations, a Cartesian coordinate system x-y-z is used on the workpiece in FIG. 3. It is apparent that the described dimensions and movements may also be represented in other coordinate or reference systems.

[0043] FIG. 3 shows a straight-toothed bevel gear 2 and a detail of a disk-shaped grinding tool 4. The grinding is carried out by discontinuous generating grinding. Here, for example, a workpiece rotation of the bevel gear 2 around the z axis is overlaid with a movement of the grinding tool 4, which corresponds to the movement of a tooth of a virtual generator crown gear, so that the disk-shaped grinding tool 4 and the straight-toothed bevel gear 2 roll on one another in a known manner. The grinding tool 4 rotates around a tool axis of rotation 6 during this.

[0044] Due to the grinding, a radius of curvature results in the gap base 8 of a respective tooth 10 of a straight toothing 12 of the bevel gear 4. No pendulum stroke takes place along a tooth width B. The radius of curvature in the gap base essentially corresponds to the outer radius r of the disk-shaped grinding tool 4 and remains on the finished bevel gear 2.

[0045] A longitudinal crowning is generated on the straight toothing 12 of the bevel gear 2 by the grinding (FIG. 4, FIG. 5). FIG. 4 shows a section in a plane which has the indicated radius r and axis 6 according to FIG. 3. The absolute value L of the longitudinal crowning is a maximum deviation of a flank line 14 of a tooth 10 from a straight line G here, as shown in FIG. 5, which schematically represents a section III-III according to FIG. 3 and shows the longitudinal crowning L along the tooth width B.

[0046] The straight line G represents by way of example here a linear, non-longitudinally-crowned flank line, for example, at the height of the pitch cone of the bevel gear 2 corresponding to section III-III. The maximum deviation is typically located in the region of a toe 20 or heel 22 of a tooth 10 (FIG. 3).

[0047] The longitudinal crowning L is generated in that a cutting face 16 of the grinding tool rotates relative to the bevel gear 2 at a hollow cone angle γ. FIG. 6 and FIG. 7 show the fundamental relationship between the hollow cone angle γ and a radius r.sub.0 of the grinding tool 4 for a predetermined radius of curvature r.sub.kr of the longitudinal crowning. The cutting face 16 forms a section of a hollow cone inner surface 16, wherein a corresponding hollow cone 18 is indicated by the dashed lines in FIG. 6. The angles have been changed in FIG. 7 in comparison to FIG. 6 in order to shrink the sketch of FIG. 7.

[0048] The grinding tool 4 is a dressable grinding tool 4.

[0049] According to the described method, a plurality of bevel gears 2 is produced using the grinding tool 4, wherein dressing of the grinding tool 4 is carried out between the machining of the bevel gears 2. It can thus be provided that a first number of the plurality of bevel gears 2 is machined, the grinding tool 4 is then dressed, and subsequently a second number of the plurality of bevel gears 2 is machined using the dressed grinding tool 4, etc. Repeated dressing of the grinding tool 4 can thus take place during the machining of the plurality of bevel gears 2.

[0050] In the present case, at least one first bevel gear 2′ of the bevel gears 2 is ground before the dressing by means of the dressable grinding tool 4 and at least one second bevel gear 2″ of the bevel gears 2 is ground after the dressing by means of the dressable grinding tool 4 (FIG. 8, FIG. 9).

[0051] During the dressing of the dressable grinding tool 4, a radius of the grinding tool 4 is reduced by the dressing from a first radius r.sub.01 to a second radius r.sub.02.

[0052] The cutting face 16 of the grinding tool 4 forming the section of the hollow cone inner surface 16 is inclined before the dressing by a first hollow cone angle γ.sub.1 and is inclined after the dressing by a second hollow cone angle γ2.

[0053] The radius of curvature r.sub.kr of the longitudinal crowning is constant before and after the dressing, so that essentially the same longitudinal crowning is generated before and after the dressing.

[0054] The following applies:

[00002]${\gamma }_2=\mathrm{arc}\sin \left(\frac{r_{02}}{r_{01}}.Math.\sin {\gamma }_1\right);$

with r.sub.01 as the first radius of the grinding tool, with r.sub.02 as the second radius of the grinding tool, with γ.sub.1 as the first hollow cone angle, and with γ.sub.2 as the second hollow cone angle.

[0055] Hollow cones 18′ and 18″ are shown in each case in FIGS. 8 and 9, which each result from an extension of the cutting face 16 toward the axis of rotation 6.

[0056] To compensate for the circumstance that the radius of the grinding tool is reduced with each dressing procedure, the grinding tool 4 is therefore pivoted with decreasing radius in the direction of the bevel gear 2 in the present example, i.e., the hollow cone angle is reduced, so that essentially the same longitudinal crowning can still be produced.

[0057] Further dressing procedures can be carried out according to the same pattern, wherein hollow cone angles γ.sub.3, γ.sub.4, γ.sub.5 . . . can be generated corresponding to the radii r.sub.03, r.sub.04, r.sub.05 . . . reduced by the dressing.

[0058] A tool flank angle α.sub.1 of the tool 4 is reduced upon dressing by the difference of the first angle of inclination γ.sub.1 to the second angle of inclination γ.sub.2, so that upon dressing the tool flank angle α.sub.2 is dressed, so that before or after the dressing the same engagement angle of the bevel gear toothing is generated on the first and second bevel gear 2′, 2″.

[0059] A sequence of a method according to the disclosure thus results as follows, for example: in a first method step (a) a first bevel gear 2′ or a number of first bevel gears 2′ is machined using the grinding tool 4, wherein the grinding tool 4 has the first radius r.sub.01 and the first hollow cone angle γ.sub.1 is predetermined for generating a longitudinal crowning having a radius of curvature r.sub.kr. The grinding takes place in discontinuous generating grinding, so that the two flanks are machined in succession in sequential infeeds.

[0060] Right flanks of the respective straight toothing of a respective bevel gear 2′ are machined in a first infeed using first machine settings and left flanks of the respective straight toothing of a respective bevel gear 2′ are machined in a second infeed using second machine settings.

[0061] Subsequently, in method step (b), dressing of the grinding tool 4 takes place, wherein the dressing takes place in such a way that after the dressing in a method step (c), a second bevel gear 2″ or a number of second bevel gears 2″ is generated using the dressed grinding tool 4, the longitudinal crowning of which after the dressing essentially corresponds to the longitudinal crowning before the dressing.

[0062] For this purpose, in the design of the dressing procedure, the radius of curvature r.sub.kr is specified as constant and the hollow cone angle γ.sub.2 is adapted in accordance with the reduced radius r.sub.02, using the above-mentioned rule

[00003]${\gamma }_2=\mathrm{arc}\sin \left(\frac{r_{02}}{r_{01}}.Math.\sin {\gamma }_1\right).$

The absolute value L of a longitudinal crowning of the straight toothing of the first bevel gear 2′ generated by the grinding corresponds to the absolute value of the longitudinal crowning of the straight toothing of the second bevel gear 2″ generated by the grinding.

[0063] The shape of the longitudinal crowning of the first bevel gear can deviate from the shape of the longitudinal crowning of the second bevel gear. This is illustrated in FIG. 10. Before the dressing, a point of the cutting face 16 moves in relation to the tooth flank to be ground, for example, along the ellipse E1 and after the dressing along the ellipse E2.

[0064] The same longitudinal crowning results according to absolute value, since the maximum distance along the tooth width B is L in both cases. The shape of the flank line deviates minimally from one another, however, as the detail Z shows in magnified form. This deviation, which can be mathematically computed, typically moves in the low single-digit micrometer range or is less than 1 micrometer, so that this deviation is negligible against the background of typical manufacturing tolerances.