Method for grinding a gear or profile of a workpiece

Abstract

The invention relates to a method for grinding the teeth of a workpiece using a profile grinding wheel, wherein all tooth gaps (1, 2, 3, 4, 5, ...) of the teeth are successively ground using the profile grinding wheel. To further develop such a method so that the ground workpiece with its teeth exhibits the lowest possible tendency to excite vibrations during subsequent operation, the invention provides that the grinding of the tooth gaps is carried out by the following sequence of steps: a) Dividing all tooth gaps to be ground into several groups (G1, G2, G3, ...) wherein each group comprises a number of adjacent tooth gaps; b) grinding down all tooth gaps of a first group (G1), wherein a sequence is defined for grinding down the individual tooth gaps of the first group, which is designed in such a way that at least for some of the tooth gaps it is ensured that two immediately adjacent tooth gaps are not ground down immediately one after the other; c) performing step b) for all further groups (G2, G3, ...) until all tooth gaps of all groups (G1, G2, G3, ...) have been ground down.

Description

[0001] The invention relates to a method for grinding a toothing or a profile of a workpiece by means of a profile grinding wheel, wherein all tooth or profile gaps of the toothing or profile are ground one after the other by means of the profile grinding wheel.

[0002] This generic method is used particularly for grinding larger gears with a large number of teeth and thus a corresponding number of tooth gaps. In this process, the individual tooth gaps are ground one after the other using the profile grinding wheel over several cycles until all tooth gaps have been machined. With a sufficiently large number of teeth, it is necessary to dress, i.e., re-profile, the profile grinding wheel after a certain number of tooth gaps have been ground.

[0003] Typically, this procedure is followed, particularly during the final pass (i.e., the finishing pass), in which the individual tooth gaps are continuously ground in the circumferential direction of the gearing. The disadvantage of this is that the periodic dressing of the profile grinding wheel results in systematic patterns in the gearing, which lead to undesirable audible or perceptible vibrations during subsequent gear operation. Certain orders of vibration (harmonics) are sometimes amplified, which can also lead to amplified tonal components in the noise, which in turn increases the disturbance to human perception.

[0004] It is also known here to machine the subsequent tooth gaps starting from an initial tooth gap in such a way that the adjacent tooth gaps in both circumferential directions are machined sequentially. This means that after grinding an initial tooth gap, the workpiece is rotated in the circumferential direction to the next tooth gap and this is machined. The workpiece is then rotated back in the opposite direction to the previous direction of rotation to the next, as yet unground tooth gap and this is machined. This process is continued until all of the tooth gaps have been ground. This can slightly reduce the tonal components of the noise; however, the machining time is considerably longer because the workpiece must undergo correspondingly large rotary movements during machining until all of the tooth gaps have been machined.

[0005] However, the latter approach can already minimize gear pitch deviations to a certain extent. These deviations arise, for example, from tool wear, heat exposure, and machine compliance. Furthermore, they are also subject to systematic influences, such as the manufacturing technology and machining sequence, as well as the frequency of intermediate dressing of the grinding wheel.

[0006] The invention is based on the object of developing a method of the type mentioned above in such a way that, on the one hand, the ground workpiece with its gearing or profile exhibits the lowest possible tendency to excite vibrations during subsequent operation, and, on the other hand, that the grinding of the workpiece is carried out in the shortest possible time, thus maximizing the cost-effectiveness of the method. Furthermore, reproducibility for similar workpieces is to be ensured. Attention is also paid to ensuring that the method can be carried out without significant computational effort and, in particular, that a detailed measurement of the gear prior to grinding is dispensed with.

[0007] The solution to this problem by the invention is characterized in that the grinding of the tooth or profile gaps is carried out by the sequence of the following steps: a) dividing all tooth or profile gaps to be ground into several groups of gaps, each group comprising a number of tooth or profile gaps, the tooth or profile gaps of each group forming a circumferential section of the toothing or profile, the groups directly adjoining or overlapping one another over the circumference of the toothing or profile and in their entirety comprising all tooth or profile gaps to be ground; b) grinding all tooth or profile gaps of a first group, wherein a sequence is defined for the grinding of the individual tooth or profile gaps of the first group, which sequence is designed in such a way that at least for some of the tooth or profile gaps it is ensured that two immediately adjacent tooth or profile gaps are not ground immediately one after the other; c) Repeat step b) for all other groups until all tooth or profile gaps of all groups have been ground.

[0008] Preferably, according to step a), all tooth or profile gaps to be ground are divided into several groups of gaps, wherein each group comprises a number of adjacent tooth or profile gaps and the groups adjoin one another over the circumference of the toothing or profile and, in their entirety, comprise all tooth or profile gaps to be ground. After this, the aforementioned groups directly adjoin one another and thus form the entire circumference of the toothing or profile. However, as stated above in step a), an overlapping arrangement can also be provided in that one or more tooth or profile gaps are omitted when defining a group and are then assigned to a subsequent group.

[0009] In the latter case, i.e. when one or more tooth or profile gaps are omitted to define the group, the circumferential extent of a group is preferably less than 180° of the circumference of the toothing or profile, particularly preferably less than twice the number of tooth or profile gaps of the group.

[0010] It is preferably provided that the sequence of machining the tooth or profile gaps according to step b) and step c) above is different in at least two of the groups, preferably in all groups. Accordingly, the chronological order in which the tooth or profile gaps of the different groups are ground is different.

[0011] One possibility in this regard is to mirror the processing order in two different groups. Shifting the processing order is also possible.

[0012] The portion of the tooth or profile gaps according to step b) above for which two directly adjacent tooth or profile gaps are not ground immediately one after the other is preferably at least 30%, particularly preferably at least 50%, and most particularly preferably at least 75% of all tooth or profile gaps. Therefore, while it is not ruled out that two directly adjacent tooth or profile gaps may be ground immediately one after the other, this preferably does not apply to the majority of the gaps.

[0013] It is preferable to dress or intermediately dress the profile grinding wheel at least once during the grinding of all tooth or profile gaps.

[0014] The number of dressing operations of the profile grinding wheel during the grinding of all tooth or profile gaps preferably corresponds to the number of groups. In particular, it can be provided that the profile grinding wheel is dressed before the tooth or profile gaps of a group are ground. Another possible embodiment provides for two groups to be ground per dressing operation.

[0015] A further development requires that the number of tooth or profile gaps differ between at least two groups. In this case, it can be stipulated, in particular, that the number of tooth or profile gaps differ between at least 50% of all groups.

[0016] Preferably, at least 75% of all groups have between 5 and 40 tooth or profile gaps.

[0017] The method is used particularly advantageously when the toothing or profile has at least 40, preferably at least 60 and particularly preferably at least 100 tooth or profile gaps.

[0018] Furthermore, the method is advantageous if the grinding of the gear requires more than two dressings in the finishing cycle due to the number of teeth and gear width.

[0019] The advantage of the proposed method is that it allows for a seemingly random grinding sequence of the tooth or profile gaps. However, by dividing the gears into groups and grinding the individual tooth gaps within a group in the manner described, this sequence is not random but can be quickly and easily determined using a simple algorithm. Nevertheless, the gear produced in this way tends to have a lower tonal and sonic noise, thus resulting in a more pleasant psychoacoustic perception.

[0020] On the other hand, the proposed procedure minimizes the time required to rotate the gear into the appropriate position for grinding a tooth gap.

[0021] Overall, this results in an improved and more pleasant psychoacoustic behavior of the manufactured gear while at the same time making production faster and therefore more economical.

[0022] The drawing shows embodiments of the invention. Fig. 1 shows schematically the tooth gaps to be ground of a gear with a total of 78 teeth and thus 78 tooth gaps to be ground, whereby the total number of tooth gaps is divided into a total of eight groups (G1 to G8), Fig. 2 shows schematically the grinding sequence of a group with 11 tooth gaps and Fig. Figure 3 shows schematically the grinding sequence of a group with 10 tooth gaps.

[0023] In Fig. Figure 1 schematically shows a gear wheel having 78 teeth and thus 78 tooth gaps to be ground; the tooth gaps are numbered accordingly.

[0024] In the illustrated example, the total of 78 tooth gaps to be ground are divided into 7 groups of 11 tooth gaps each, with the groups adjoining one another in the circumferential direction. As can be seen, however, the groups do not follow one another circumferentially, but are arranged at different points along the circumference. In the illustrated example, an eighth group remains with the last tooth gap (number 78).

[0025] All 78 tooth gaps must be finally ground (i.e. by finishing grinding) using a profile grinding wheel (not shown).

[0026] The procedure is that before the grinding process, an algorithm that is stored in the machine control and works there, divides the 78 tooth gaps into the Fig. 1 outlined groups G1 to G8. In the simplest case (as in Fig. 1), each group is given a fixed number of tooth gaps to be ground, in this case 11 tooth gaps to be ground (which is why in the example shown group G8 remains with the remaining single tooth gap).

[0027] It is important that the profile grinding of the individual tooth gaps is carried out in such a way that the individual groups G1 to G8 with their respective tooth gaps are machined one after the other. Fig. Incidentally, Figure 1 indicates that the individual groups G1 to G8 do not necessarily have to be arranged one after the other in the circumferential direction of the gearing. Different circumferential areas of the gearing can be machined one after the other.

[0028] As can be seen from Fig. 1 and the numbering of the individual tooth gaps, the procedure is not such that the individual tooth gaps of a group are machined one after the other in the circumferential direction, but rather that the grinding of the individual tooth gaps of a group is carried out in such a way that only as few directly adjacent tooth gaps as possible are machined one after the other. For the majority of tooth gaps, preferably at least 75%, it should therefore be ensured that two directly adjacent tooth gaps are not ground one after the other.

[0029] What this can look like in concrete terms is described in the Fig. 2 and Fig. 3 is illustrated as an example.

[0030] In Fig. 2 initially outlines the case where a group with 11 tooth gaps (1 to 11) is machined, ie a group with an odd number.

[0031] The algorithm stored in the machine control system can proceed in such a way that the middle of the tooth gaps (tooth gap 6) is machined first. The algorithm then initiates the grinding of the first tooth gap in the group (tooth gap 1) and then the last of the tooth gaps (tooth gap 11). The unground tooth gaps 2 to 5 are then machined, with the middle tooth gap of these remaining tooth gaps (rounded down to the whole number here, i.e. tooth gap 3) being ground first. Subsequently, tooth gap 2, then tooth gap 5 and finally tooth gap 4 are ground. This ensures that as few immediately adjacent tooth gaps as possible are ground one after the other and, above all, that the distance between subsequently ground gaps varies as much as possible. The distances between the successively ground gaps are therefore de facto irregular.The algorithm then initiates the grinding of the remaining tooth gaps 7 to 10 in an analogous manner.

[0032] In Fig. 3 shows the case where a group with 10 tooth gaps (1 to 10) is machined, ie a group with an even number.

[0033] Here, the algorithm first initiates the grinding of the middle tooth gap (gap 5), rounding down to the nearest whole number. Then, the first tooth gap (gap 1) is ground again, followed by the last tooth gap (gap 10). This is followed by the machining of the tooth gaps to be ground in the "front" interval of gaps 2 to 4, with the middle tooth gap 3 being ground first, then the preceding tooth gap 2, and then the remaining tooth gap 4. This is followed by the machining of the tooth gaps to be ground in the "back" interval of gaps 6 to 9, starting with gap 8 and continuing with gap 6, gap 9, and finally gap 7.

[0034] Out of Fig. 3 shows that only once were two adjacent tooth gaps ground one after the other (namely tooth gap 2 after tooth gap 3).

[0035] Nevertheless, both the procedure according to Fig. 2 as well as the one according to Fig. 3 ensures that the idle time for rotating the gear to the corresponding tooth gaps to be ground remains as short as possible.

[0036] From the presentation of the Fig. 2 and Fig. 3 shows that a relatively simple algorithm can be used to determine the grinding sequence of the individual tooth gaps in a group, which, after determining the size of the individual groups, can determine the grinding sequence without having to have any further information.

[0037] In the exemplary embodiment, the procedure is such that the middle tooth gap (if there is an even number of tooth gaps: the middle tooth gap rounded downwards) of the group to be machined is ground first. Then the first and then the last tooth gap are machined. The front remaining interval of tooth gaps is then machined, where the middle one (if there is an even number of tooth gaps: the tooth gap rounded downwards) is ground first. Then the adjacent tooth gaps are machined. The same procedure is then applied to the rear remaining interval of tooth gaps. This ensures that as few tooth gaps located directly next to one another as possible are ground one after the other.

[0038] Furthermore, this procedure also results in jumps of different sizes between the individual tooth gaps of a group, which is advantageous for an irregular distribution of remaining inaccuracies and thus for a lower vibration excitation of the gear during later operation.

[0039] Preferably, each group, or at least as many groups as possible, is ground in a different sequence. This can be achieved by mirroring or shifting the order between two groups, for example.

[0040] This effect, ie the most irregular distribution of remaining inaccuracies, can be further improved if the individual groups of tooth gaps to be ground are of different sizes. While, as explained above, in the exemplary embodiment according to Fig.1 always formed groups with 11 tooth gaps, this can of course also be done differently, so that, for example, groups are ground that have 8 to 15 tooth gaps.

[0041] Before grinding each group of tooth gaps, a dressing process for the profile grinding wheel can be scheduled. However, this is only a preferred and not mandatory procedure.

[0042] Overall, the proposed procedure results in a ground gear or a ground profile that exhibits a virtually purely statistically distributed irregularity regarding remaining pitch errors without complex measures (measurement of pitch errors, computationally intensive algorithms). Such a gear tends to exhibit more pleasant or improved NVH (noise vibration harshness) behavior during subsequent operation. It can therefore be said that, thanks to the proposed method, the finished ground gear exhibits pitch errors that appear random, even though they are actually reproducibly achieved using the described procedure.

[0043] Another great advantage is that identical gears are always ground in the same way, making transferability between multiple grinding machines easy. This ensures a high degree of reproducibility.

[0044] Grinding does not require complex or computationally intensive calculations; no mathematical problems (such as solving equations or optimization problems) need to be solved. Special data, such as expected pitch deviations or similar assumptions, are also not required.

Claims

[1] Method for grinding a toothing or a profile of a workpiece by means of a profile grinding wheel, wherein all tooth or profile gaps (1, 2, 3, 4, 5, ...) of the toothing or the profile are ground one after the other by means of the profile grinding wheel, characterized by that the grinding of the tooth or profile gaps is carried out by the sequence of the following steps: a) dividing all tooth or profile gaps to be ground into a plurality of groups (G1, G2, G3, ...) of gaps, each group (G1, G2, G3, ...) comprising a number of tooth or profile gaps, the tooth or profile gaps of each group (G1, G2, G3, ...) forming a circumferential section of the toothing or profile, the groups (G1, G2, G3, ...) directly adjoining one another or overlapping one another over the circumference of the toothing or profile and comprising in their entirety all tooth or profile gaps to be ground; b) grinding all tooth or profile gaps of a first group (G1), wherein a sequence is defined for the grinding of the individual tooth or profile gaps of the first group, which sequence is designed in such a way that at least for some of the tooth or profile gaps it is ensured that two immediately adjacent tooth or profile gaps are not ground immediately one after the other; c) Carry out step b) for all other groups (G2, G3, ...) until all tooth or profile gaps of all groups (G1, G2, G3, ...) have been ground. [2] Method according to claim 1, characterized by that in at least two of the groups (G1, G2, G3, ...) the sequence of machining the tooth or profile gaps according to step b) and step c) of claim 1 is different. [3] Method according to claim 2, characterized bythat in all groups (G1, G2, G3, ...) the sequence of machining the tooth or profile gaps according to step b) and step c) of claim 1 is different. [4] Method according to one of claims 1 to 3, characterized by that the part of the tooth or profile gaps according to step b) of claim 1, for which two immediately adjacent tooth or profile gaps are not ground immediately one after the other, amounts to at least 30%, preferably at least 50% and particularly preferably at least 75% of all tooth or profile gaps. [5] Method according to one of claims 1 to 4, characterized by that the profile grinding wheel is dressed at least once during the grinding of all tooth or profile gaps. [6] Method according to claim 5, characterized by that the number of dressing operations of the profile grinding wheel during grinding of all tooth or profile gaps corresponds to the number of groups. [7] Method according to claim 6, characterized by that the profile grinding wheel is dressed before the tooth or profile gaps of a group are ground. [8] Method according to one of claims 1 to 7, characterized by that the number of tooth or profile gaps differs in at least two groups. [9] Method according to claim 8, characterized by that the number of tooth or profile gaps differs in at least 50% of all groups. [10] Method according to one of claims 1 to 9, characterized by that at least 75% of all groups have between 5 and 40 tooth or profile gaps. [11] Method according to one of claims 1 to 10, characterized by that the toothing or profile has at least 40, preferably at least 60 and particularly preferably at least 100 tooth or profile gaps.

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