Method for grinding a tooth or profile of a workpiece

Abstract

The invention relates to a method for grinding a tooth (1) of a workpiece (2) by means of a profile grinding wheel (3), wherein the workpiece (2) has an axis of rotation (a), wherein the grinding wheel (3) has an axis of rotation (b) and a center (M), which lies on the axis of rotation (b) of the grinding wheel (3) and in the middle of the axial length (e) of the grinding wheel (3), and wherein the workpiece (2) has an end face (7) at least in an axial end region (5, 6) of the tooth (1) or of the profile. In order to produce an axial end of a burr-free tooth in a simple and precise manner, the invention provides that the grinding of the tooth (1) comprises the following steps: (a) grinding of the tooth gaps (4) of the workpiece (2) by means of the profile grinding wheel (3); b) grinding of a plurality of chamfers (9) in the region of the axial ends (8) of the tooth gaps (4) by the grinding wheel (3), wherein the grinding wheel (3) at least temporarily assumes a position during the grinding of the chamfers (9), in which the grinding wheel (3) is arranged relative to the workpiece (2) such that the axial ends (8) of the tooth gaps (4) are in contact with the grinding wheel (3), wherein, in a projection onto a plane containing the axis of rotation (a) of the workpiece (2) and the center (M) of the grinding wheel (3), an angle (δ) between the axis of rotation (a) of the workpiece (2) and a connecting line (RV) between the axial end of the tooth gap (8) and the center (M) is contained between 20° and 70°.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for grinding a tooth or profile of a workpiece by means of a grinding wheel, wherein the grinding wheel is designed as a profile grinding wheel and is guided through a pre-machined tooth or profile gap or generates a tooth or profile gap, wherein the workpiece has an axis of rotation, wherein the grinding wheel has an axis of rotation and a center lying on the axis of rotation of the grinding wheel and extending axially from the center, and wherein the workpiece has an end face at least in an axial end region of the tooth or the profile. BACKGROUND

[0002] DE 43 97 508 T1 discloses a method of the general type. Similar solutions are shown in DE 37 21 949 A1 and DE 10 2008 036 549 A1.

[0003] In the manufacture of teeth and similar profiles, it is common practice to first machine the basic shape of the tooth to be produced from a blank into the material which has not yet been hardened by a pre-machining process, for example hobbing; that is, the tooth space is initially prefabricated in this respect. Depending on the size of the workpiece and the batch size, this can be followed by a machining step in which the end face chamfer is machined. In the case of smaller batches and larger workpieces, it is known to apply the end face chamfer manually in a more or less defined manner, for which purpose, in particular, an angle grinder or axial grinder is used. Sometimes special equipment is also used to produce the end face chamfer by machine in a separate operation. This is followed by the hardening of the workpiece and the prefabricated tooth. The final hard machining is then carried out by grinding, in particular by profile grinding.

[0004] After grinding the tooth, in particular in the case of involute teeth, burr formation and / or sharp edges can occur at the face end of the tooth, in particular in the case of a large amount of material being removed. This requires appropriate reworking, in particular by hand. If these gear teeth or profiles are ground as solids, i.e. if there is no pre-machining, in particular by hobbing, but instead the gear teeth or profiles are machined from a cylindrical blank by grinding, this problem occurs to a certain extent. SUMMARY

[0005] The invention is based on the object of further developing a method of the general type which makes it possible to remove a burr from the axial end of a tooth or profile in a simple and precise manner and to apply a defined chamfer there.

[0006] The solution to this object is provided by the invention, which grinding of a tooth or profile comprises the following steps:

[0007] a) grinding a tooth or profile gap of a workpiece by means of a profile grinding wheel;

[0008] b) grinding the chamfers by means of the grinding wheel in the region of the axial end of the tooth or profile gap, wherein the grinding wheel is arranged in a position in which, during grinding of the chamfers, or at least temporarily, the grinding wheel is arranged relative to the workpiece such that the axial end of the tooth or profile gap touches the grinding wheel, wherein in a projection onto a plane which comprises the rotational axis of the workpiece and the center of the grinding wheel, an angle between the rotational axis of the workpiece and the connecting line between the axial end of the tooth or profile gap and the center is comprised between 20° and 70°.

[0009] According to a preferred embodiment of the application, the profile grinding wheel is a dressable grinding wheel, wherein after carrying out the above-mentioned step a) and before carrying out the above-mentioned step b), the profile of the grinding wheel is changed by a dressing operation. Thus, the profile of the grinding wheel is changed from the profile required for grinding the tooth or profile to a profile in which the chamfers can be ground to the desired shape.

[0010] When carrying out the above-mentioned step a), it can be advantageous in preferred applications to grind the tooth or profile gap from the solid.

[0011] The above-mentioned step b) is preferably carried out by relative lateral feed between the workpiece and the grinding wheel. The step can also be carried out in such a way that the grinding wheel is guided perpendicular to the connecting line relative to the workpiece. Of course, it is also possible to move the grinding wheel under NC control along a predetermined path in order to grind the chamfers.

[0012] The above-mentioned angle is preferably between 35° and 55°.

[0013] A possible embodiment of the method is that, when grinding the chamfers, a plane through the center of the grinding wheel and perpendicular to the rotational axis of the grinding wheel is aligned with the tooth or profile gap (see the embodiment according to Figure 1 the following explanation).

[0014] Alternatively, it is also possible that, during grinding of the chamfers, a plane through the center of the grinding wheel and perpendicular to the rotational axis of the grinding wheel is pivoted away from alignment with the tooth or profile gap by an angle. This angle is preferably between 2° and 25° (see the embodiment according to Figure 5 the following explanation). In particular, in the case of grinding a helical gear, the angle is between 2° and the helix angle of the tooth.

[0015] A further alternative embodiment of the method provides that, when grinding the chamfers, the projection of the rotational axis of the grinding wheel onto the center plane of the workpiece (comprising the rotational axis of the workpiece) has an angle of 90° between the rotational axis of the workpiece. In this case, the grinding wheel is displaced in the direction of its rotational axis in such a way that the axial end of the tooth or profile gap touches the grinding wheel (see the embodiment according toFigure 4 In this case, it has proven useful if the grinding wheel is shaped in such a way that it has an asymmetric profile. This makes it possible to grind the chamfer into an optimum or desired shape.

[0016] The chamfer is usually ground at the axial ends of all toothing or profile gaps. It is usually also ground in the two axial end regions of the workpiece.

[0017] With the proposed procedure, the chamfer of a tooth or profile can be defined on the front face by means of a profile grinding wheel which is additionally used for grinding the tooth or profile itself.

[0018] The proposed method is particularly preferably used for the production of involute toothing. However, it can also be used for other gearings or profiles.

[0019] The method thus allows the use of a profile grinding wheel used in the special grinding position defined above to apply the desired chamfer to the workpiece in a controlled and repeatable manner. According to the above preferred embodiment of the application, the geometry of the chamfer to be ground can be defined within certain limits according to predetermined wishes if the grinding wheel is dressed to a modified profile before the grinding of the chamfer.

[0020] The profile grinding wheel used for grinding the tooth or profile is thus also used, after appropriate positioning, to grind the chamfer into the axial end regions of the tooth or profile gap, in particular by combining the radial and axial movement of the grinding wheel relative to the workpiece (by appropriate use of the NC axes of the machine). In this case, the positioning or adjustment, in particular with regard to the above-mentioned angle, is carried out according to the specifications required by the chamfer design. In this way, it can be specifically achieved that the chamfer is ground uniformly and in particular parallel to the face of a pre-toothed helical gear.

[0021] The method is particularly advantageous for small series production or the production of large workpieces, whereby after the actual grinding process (possibly divided into rough and fine grinding, grinding into solid is also possible), the face chamfer is applied to the gear teeth in a defined manner.

[0022] In principle, the method can be used for involute gearings as well as other types of gearing.

[0023] Advantageously, the method is carried out as part of or directly after grinding the tooth or profile of the workpiece in the same clamping.

[0024] The method is particularly advantageous for large workpiece sizes and a large number of teeth on the teeth. BRIEF DESCRIPTION OF DRAWINGS

[0025] Embodiments of the application are shown in the drawings.

[0026] Figure 1A gear is shown in perspective view and according to a first embodiment of the application, in the axial end region of which a chamfer is ground by means of a profile grinding wheel,

[0027] Figure 2 A gear wheel according to a second embodiment of the application is shown in perspective view, in the axial end region of which the chamfer is ground by means of the profile grinding wheel,

[0028] Figure 3 The axial end region of a gear with ground chamfer is shown in perspective view and enlarged view,

[0029] Figure 4 A gear according to a third embodiment of the application is shown in perspective view, in the axial end region of which the chamfer is ground by means of the profile grinding wheel, and

[0030] Figure 5 A perspective view of a gear according to a fourth embodiment of the application is shown, in the axial end region of which the chamfer is ground by means of the profile grinding wheel.

[0031] List of Markings

[0032] 1 tooth (profile)

[0033] 2 workpiece

[0034] 3 profile grinding wheel

[0035] 4 pre-machined tooth or profile gap

[0036] tooth or profile gap to be produced

[0037] 5 axial end region of a tooth or profile

[0038] 6 axial end region of a tooth or profile

[0039] 7 end face

[0040] 8 axial end of a tooth or profile gap

[0041] 9 chamfer

[0042] a rotational axis of the workpiece

[0043] b rotational axis of the grinding wheel

[0044] M centre of the grinding wheel

[0045] e axial extension of the grinding wheel

[0046] f root circle of a tooth or profile

[0047] RV is the line connecting the axial ends of the tooth or profile gap and its center.

[0048] δ angle

[0049] ε rotation angle DETAILED DESCRIPTION

[0050] Figure 1 A workpiece 2 in the form of a gear is shown, having teeth 1. The teeth 1 have pre-formed tooth gaps 4 (only one of which is shown; the others are evenly distributed around the circumference of the workpiece 2). A profile grinding wheel 3 is used to grind the teeth 1. This passes through the tooth gap 4 at a predetermined distance between the workpiece 2 and the grinding wheel 3 in a known manner to give the tooth gap the desired final profile (i.e., the tooth is machined using profile grinding).

[0051] The tooth 1 has two axial end regions 5 and 6; here, two end faces 7 abut (at Figure 1 Only the front end face can be seen in the figure). In the area of ​​the axial end 8 of the tooth gap 4, grinding can lead to the formation of interfering burrs. Furthermore, a defined chamfer arrangement is required. To produce this product automatically by machine, the following procedure is used:

[0052] First, but not shown, the grinding wheel 3 is dressed again to the profile specified for the desired chamfer (see Figure 3 ).

[0053] Then, the profile grinding wheel 3 that has ground the tooth gap 4 is moved to the position as shown in FIG. Figure 1 Position shown.

[0054] The axial ends 8 of the tooth gaps 4 are therefore located in the immediate vicinity of the grinding wheel 3. As regards the position of the grinding wheel 3 relative to the workpiece 2, this results in that, in projection onto a plane containing the axis of rotation a of the workpiece 2 and the center M of the grinding wheel 3, the axis of rotation a of the workpiece 2 and the connecting line RV between the axial ends of the tooth or profile gaps 8 and the center M comprise an angle δ, which is angularly spaced according to Figure 1 In the embodiment of FIG. 5 , the angle is approximately 45°.

[0055] In this case, the center M of the grinding wheel 3 is formed as a point on the rotation axis b of the grinding wheel, which point is located in the center of the axial extension e of the grinding wheel.

[0056] The connection line RV is obtained when the grinding wheel 3 just contacts the axial end of the tooth gap 4, as shown in FIG. Figure 1 and Figure 2 For exact positioning of the axial ends of the teeth or profile gaps 8, see Figure 2 , in which the root circle f of the tooth 1 is shown; where the root circle f reaches the axial end of the workpiece 2, the axial end 8 of the tooth or profile gap is provided.

[0057] Once the explained position has been reached, the chamfer is ground by the profile wheel 3, wherein the wheel 3 is suitably advanced or guided along a predetermined path with respect to the workpiece 2. The result of this process is shown in Figure 3 , wherein the chamfer 9 ground in this way is shown at the axial end of the profile gap 4.

[0058] Figure 1 The case is shown in which a straight-toothed workpiece 2 is subjected to the application of a chamfer. It can be seen how the profile wheel 3 is aligned with the tooth gap 4 when the chamfer 9 is ground.

[0059] With regard to the alignment, it should be noted that a plane is first defined which contains the rotation axis a of the workpiece; the rotation axis b of the wheel is displaced or projected until it is flush with the rotation axis a of the workpiece; the rotation axis a and the displaced or projected rotation axis b form said plane. The alignment occurs when the direction of the tooth or profile gap, projected into said plane (at an axial offset from the workpiece 2), and the direction perpendicular to the rotation axis b, also projected into said plane, do not include an angle (or zero degrees).

[0060] This alignment also exists in the embodiment shown in Figure 2 . This differs from the case between Figure 1 in that it involves grinding helical teeth. Otherwise, it is the same as described in connection with Figure 1 . In particular, it is again apparent from Figure 2 that, before the chamfer 9 is ground, the profile wheel 3 is brought into said position (see angle δ).

[0061] In the embodiment shown in Figure 4 , the profile wheel 3 is not aligned with the tooth space 4. Rather, the wheel 3 is moved in the direction of its rotation axis b (while the workpiece 2 is correspondingly rotated about its axis a) until the positional relationship as in the case of Figure 1 and 2 is established again. Working without alignment (according to Figure 1 and 2 ) has the advantage of advantageously applying the chamfer 9 under given conditions. In this regard, the embodiment according to Figure 4 represents a particularly preferred solution according to the invention.

[0062] Finally, according to given conditions, it can be advisable to grind the chamfer 9 as shown in the embodiment of Figure 5 .

[0063] In addition, the profile wheel 3 is not aligned with the tooth gap 4. However, now, before the chamfer 9 is ground, the profile wheel 3 has been deliberately rotated out of alignment by an angle of rotation ε. This is also very advantageous for optimizing the chamfer 9 with the desired profile of the wheel 3.

[0064] Depending on the specific application, i.e. depending on the specific geometry of the gap to be ground, it is thus possible to achieve a favorable geometry of the chamfer to be ground by positioning the grinding wheel in a misaligned manner with respect to the course of the tooth gap.

[0065] The smaller the profile or pressure angle, the smaller the formation of the chamfer, i.e. the greater the chamfer angle becomes with respect to the surface. Therefore, teeth with a large profile or pressure angle or teeth in which the available area of the profile is positioned far from the root circle of the tooth are advantageous.

[0066] The greater the curvature of the gear profile in face cutting, the greater the chamfer angle changes within the flank.

[0067] In some cases, too great a helix angle of the teeth can become problematic. This can be remedied by reducing the mounting angle or using an asymmetric profile wheel.

[0068] This provides the general possibility of applying the desired chamfer to the workpiece in a controlled manner, in particular for deburring.

[0069] The method is particularly advantageous for workpieces with a large number of teeth, since these have little or no curvature on the flanks and the available area of the profile is usually far from the root circle diameter.

[0070] Example:

[0071] A large workpiece is provided with involute toothing (number of teeth z = 291, module m = 9, width b = 260 mm). The teeth are thus ground to solid. The machining time thereof is approximately 40 hours. Then, the chamfers 9 are ground on both faces of the workpiece in the manner described above. This results in a further machining time of approximately 1.5 hours for all chamfers. In order to complete the operation, the workpiece remains in a single fixture. Only the grinding wheel 3 is reprofiled in order to grind the chamfers by dressing.

[0072] For workpieces with gear teeth having a large helix angle, it can be useful or necessary to use a grinding wheel with an asymmetric profile.

[0073] Of course, when using the proposed method, it should also be noted that, by moving the grinding wheel to the position required for grinding the chamfer (due to the strong drop of the grinding wheel), no collisions with other components (clamping device, dressing unit, components of the workpiece itself, etc.) occur.

[0074] If, due to the set angle with respect to the surface side (for grinding the chamfer) being too steep, a foreseeable grinding into the flank occurs, the set angle is set to prevent this.

[0075] It is also possible to prevent the above-mentioned (unwanted) grinding into the flank by rotating the grinding wheel (see Figure 5 , the rotation angle ε).

Claims

1. A method for grinding a tooth (1) or a profile of a workpiece (2) by means of a grinding wheel (3), wherein: The grinding wheel (3) is designed as a profile grinding wheel and is guided through pre-machined teeth or profile gaps (4) or produces teeth or profile gaps (4), wherein the workpiece (2) has a rotation axis (a), wherein the grinding wheel (3) has a rotation axis (b) and a center (M), the center (M) being located on the rotation axis (b) of the grinding wheel (3) and in the middle of the axial extension (e) of the grinding wheel (3), and wherein the workpiece (2) has an end face (7) at least in an axial end region (5, 6) of the tooth (1) or the profile, It is characterized by The grinding of the tooth (1) or the profile comprises the following steps: a) grinding the teeth or profile gaps (4) of the workpiece (2) by means of the profile grinding wheel (3); b) grinding a chamfer (9) in the region of the axial end (8) of the tooth or profile gap (4) by means of the grinding wheel (3), wherein during the grinding of the chamfer (9), the grinding wheel (3) is arranged in a position, or at least temporarily in a position, in which the grinding wheel (3) is arranged relative to the workpiece (2) so that the axial end (8) of the tooth or profile gap (4) contacts the grinding wheel (3), wherein, in a projection onto a plane comprising the rotation axis (a) of the workpiece (2) and the center (M) of the grinding wheel (3), a connecting line (RV) between the rotation axis (a) of the workpiece (2) and the axial end and the center (M) of the tooth or profile gap (4) comprises an angle (δ) between them, the connecting line (RV) being obtained when the grinding wheel (3) just contacts the axial end of the tooth or profile gap (4), the angle being between 20° and 70°, The profile grinding wheel (3) is a dressable grinding wheel, and after performing step a) and before performing step b), the profile of the grinding wheel (3) is changed by a dressing operation.

2. The method according to claim 1, characterized in that When performing step a) according to claim 1, the teeth or profile gaps (4) are solid ground.

3. The method according to claim 1, characterized in that Step b) of claim 1 is performed by performing a relative infeed between the workpiece (2) and the grinding wheel (3).

4. The method according to claim 1, wherein Step b) of claim 1 is performed by guiding the grinding wheel (3) relative to the workpiece (2) perpendicularly to the connecting line (RV) or along a predetermined path.

5. The method according to claim 1, wherein The angle (δ) is between 35° and 55°.

6. The method according to claim 1, characterized in that During grinding of the chamfer (9) according to step b) of claim 1, a plane passing through the center (M) of the grinding wheel (3) and perpendicular to the rotation axis (b) of the grinding wheel (3) is aligned with the tooth or profile gap (4).

7. The method according to claim 1, characterized in that During grinding of the chamfer (9) according to step b) of claim 1, a plane passing through the center (M) of the grinding wheel (3) and perpendicular to the axis of rotation (b) of the grinding wheel (3) is pivoted out of alignment with the tooth or profile gap (4) by a rotation angle (ε).

8. The method according to claim 7, characterized in that The rotation angle (ε) is between 2° and 25°, wherein, in particular when grinding helical teeth, the rotation angle (ε) is between 2° and the helix angle of the teeth.

9. The method according to claim 1, characterized in that When grinding the chamfer (9) according to step b) of claim 1, the angle between the projection of the rotation axis (b) of the grinding wheel (3) on the center plane of the workpiece (2) and the rotation axis (a) of the workpiece is 90°, and the center plane includes the rotation axis (a) of the workpiece (2).

10. The method according to claim 1, characterized in that The chamfers (9) are ground at the axial ends (8) of all teeth or profile gaps (4).

11. The method according to claim 1, wherein The chamfer (9) is ground in both axial end regions (5, 6) of the workpiece (2).

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