METHOD FOR MACHINING THE TOOTH FLANKS OF BEVEL GEAR WORKPIECES

Abstract

A method for machining the tooth flanks of a bevel gear workpiece includes carrying out correction machining of a concave tooth flank and a convex tooth flank of at least one tooth gap by, after machining using a first machine setting, cutting free of the concave tooth flank by the bevel gear workpiece executing a workpiece rotation in a first rotational direction having a predefined first absolute value in relation to a gear-cutting tool and/or cutting free the convex flank by the bevel gear workpiece executing a workpiece rotation in another rotational direction having a predefined second absolute value in relation to the gear-cutting tool, and finish machining the concave tooth flank using a second machine setting, which differs from the first machine setting, and finish machining the convex tooth flank using a third machine setting, which differs from the second machine setting.

Claims

1. A method for machining the tooth flanks of a bevel gear workpiece comprising the following steps: a) rotationally driving a gear-cutting tool and machining a bevel gear workpiece using a chip removal process including plunging the gear-cutting tool into the workpiece using a first machine setting up to a predefined depth into material of the bevel gear workpiece to machine a concave tooth flank and a convex tooth flank of at least one tooth gap of the bevel gear workpiece, and b) performing a correction machining the concave tooth flank and the convex tooth flank of the at least one tooth gap including (i) one or more of (1) cutting free the concave tooth flank including rotating the workpiece in a first rotational direction to an angle defined by a predefined first absolute value relative to the gear-cutting tool; or (2) cutting free the convex tooth flank including rotating the workpiece in another rotational direction to an angle defined by a predefined second absolute value relative to the gear-cutting tool, thereby enlarging a gap width of the at least one tooth gap, and (ii) finish machining the concave tooth flank using a second machine setting, which differs from the first machine setting, and (iii) finish machining the convex tooth flank using a third machine setting, which differs from the second machine setting.

2. The method according to claim 1, including performing the steps of cutting free the concave tooth flank and finish machining the concave tooth flank simultaneously and using the second machine setting.

3. The method according to claim 1, including performing the steps of cutting free the convex tooth flank and finish machining of the convex tooth flank simultaneously and using the third machine setting.

4. The method according to claim 1, further including transitioning the gear-cutting tool from the first machine setting into the second machine setting while the gear-cutting tool is partially located in the at least one tooth gap.

5. The method according to claim 1, including cutting free the concave tooth flank and cutting free the convex tooth flank, wherein the predefined first absolute value is identical to the predefined second absolute value.

6. The method according to claim 1, wherein the gear-cutting tool defines a cutter head gear-cutting tool defining bar cutters or cutter inserts, wherein each of the bar cutters or cutter inserts defines two cutting edges configured to machine the concave tooth flank and the convex tooth flank simultaneously during the step of machining the bevel gear workpiece using a chip removal process.

7. The method according to claim 1, wherein the gear-cutting tool defines a cutter head gear-cutting tool defining bar cutters or cutter inserts, wherein a part of each of the bar cutters or cutter inserts defines a cutting edge configured to machine the concave tooth flank during the step of machining the bevel gear workpiece using a chip removal process, and wherein another part of each of the bar cutters or the cutter inserts defines a cutting edge configured to machine the convex tooth flank during the step of machining the bevel gear workpiece using a chip removal process.

8. The method according to claim 1, wherein the correction machining step includes correcting flank angle errors in the workpiece oriented in a same direction that occurred during the step of machining the bevel gear workpiece using a chip removal process.

9. The method according to claim 1, further including measuring the bevel gear workpiece before performing the correction machining step, wherein the measuring step is adapted to detect flank angle errors in the workpiece.

10. The method according to claim 1, wherein the bevel gear workpiece is one bevel gear workpiece of a series of bevel gear workpieces, and the method further includes measuring the bevel gear workpiece after the step of machining the bevel gear workpiece using a chip removal process, and then subsequently performing correction machining of further bevel gear workpieces of the series of bevel gear workpieces.

11. The method according to claim 1, wherein said plunging defines a single-indexing process or a continuous-indexing process.

12. The method according to claim 11, wherein said plunging defines a continuous-indexing process, and the method further includes coupledly rotationally driving the bevel gear workpiece with said rotational driving of the gear-cutting tool.

13. The method according to claim 1, wherein the bevel gear workpiece defines a crown gear workpiece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other advantages and features of the disclosed subject matter will become apparent from the following detailed description, which are to be understood not to be limiting and which will be described in greater detail hereafter with reference to the drawings, wherein:

[0035] FIG. 1A shows a schematic side view of the machining region of a gear-cutting machine during the gear-cutting milling in a previously-known plunging method, wherein a cutter head tool is shown slightly inclined in relation to the crown gear;

[0036] FIG. 1B shows a schematic side view of the cutter head tool and the crown gear of FIG. 1A, after a plunging movement has been executed;

[0037] FIG. 1C shows a simplified, schematic illustration of a previously-known plunging method;

[0038] FIG. 2A shows a simplified, schematic illustration of a first modified plunging method;

[0039] FIG. 2B shows a simplified schematic illustration of a second modified plunging method;

[0040] FIG. 3A shows, in the lower region, a schematic top view of a crown gear workpiece and, above this, a schematic sectional illustration along normal line A-A through a tooth gap which was pre-machined by plunging in the single-indexing method;

[0041] FIG. 3B shows the schematic illustration of FIG. 3A in an enlarged form, wherein, in addition to the actual curve of the flank lines after the plunging, the setpoint curve of the flank lines is shown;

[0042] FIG. 3C shows the schematic sectional illustration of FIG. 3B, wherein in addition to the setpoint curve of the flank lines, the actual curve of the flank lines after the cutting free is shown;

[0043] FIG. 3D shows the schematic sectional illustration of FIG. 3C, wherein the final curve of the flank lines is shown.

DETAILED DESCRIPTION

[0044] Terms are used in conjunction with the present disclosure which are also used in relevant publications and patents. However, it is to be noted that the use of these terms is only to serve for better understanding. The inventive concepts and the scope of protection of the patent claims are not to be restricted in the interpretation by the specific selection of the terms. The invention may be readily transferred to other term systems and/or technical fields. The terms are to be applied accordingly in other technical fields.

[0045] Greatly varying gear-cutting tools 100 (for example, solid tools) having defined cutting edges and grinding tools (for example, cup grinding tools) can be used for machining the tooth flanks of bevel gear workpieces. Details of embodiments are described in conjunction with the following description, in which cutter head gear-cutting tools 100 are used, which comprise bar cutters or cutter inserts. A bar cutter or cutter insert can have, for example, two cutting edges, wherein one of these cutting edges is designed for the machining of the concave tooth flank 13.1 of a tooth gap 12 and the other of these cutting edges is designed for the machining of the convex tooth flank 13.2 of the tooth gap 12 in each case. The gear-cutting tools 100 can also comprise bar cutters or cutter inserts arranged in groups, however, in which one part of the bar cutters or cutter inserts have cutting edges for machining the concave tooth flank 13.1 and another part of the bar cutters or cutter inserts have cutting edges for machining the convex tooth flank 13.2.

[0046] However, what is described may also be transferred to other tools 100, which are designed for the gear cutting of bevel gear workpieces 10.

[0047] Such tools 100 and the corresponding gear-cutting machines are well known and have been used for many years in the gear cutting field.

[0048] The details of a first method are shown in summary in schematic form in FIG. 2A. This first method is also referred to here as the first modified plunging method.

[0049] The method is based in some embodiments on a classical plunging method, which was already described in conjunction with FIGS. 1A, 1B and 1C.

[0050] The dotted arrow in FIG. 2A illustrates the infeed movement ZB and the solid arrow, which is oriented in the direction of the crown gear workpiece 1 (not shown here), illustrates the plunging movement ET of the first modified plunging method.

[0051] After the tool 100 has reached the final plunging position, which is defined by the position of the tooth base on the crown gear workpiece 10, a method follows, which is referred to here as combined correction machining FB&KB. FIG. 2A indicates that the combined correction machining FB&KB comprises both cutting free FB, which is executed upon reaching or after reaching the plunging final position, and also correction machining KB, which takes place by changing/adjusting further variables of the machine setting.

[0052] The double arrow FB&KB has a slight curve in FIG. 2A, to illustrate that an adjustment of the machine setting takes place. The radius of curvature of this double arrow FB&KB is oriented in the direction of the tool 100 (not shown), to thus represent the adjustment of the machine setting. The adjustment of the machine setting is also indicated in that in addition to the double arrow FB&KB, the two machine settings M2 and M3 are mentioned in the figures.

[0053] The gap width is greater after the combined correction machining FB&KB than the tip width s.sub.a0 of the tool 100. The tip width s.sub.a0 is shown in FIG. 1B as the distance between the two cutting edges of the bar cutter 3.

[0054] The tool 100 is only drawn out of the tooth gap by a reverse-oriented movement AT after this combined correction machining FB&KB has been carried out by the adjustment of the machine settings. There is also a reversal point UP here.

[0055] Up to the execution of the reverse-oriented movement AT, in some embodiments, the tool 100 can remain a short time in the final position, so that more than only one bar cutter or cutter insert is guided in a chip-removing manner through the tooth gap.

[0056] FIG. 2B illustrates the details of a second method in schematic form in summary. Since this method is equivalent with respect to the infeed ZB, plunging ET, and withdrawal AT to the first method, reference is made in this regard to the description of FIG. 2A.

[0057] In contrast to the embodiment illustrated in FIG. 2A, the classical cutting free movements are illustrated in FIG. 2B by a separate double arrow FB. The cutting free is achieved in that the crown gear workpiece 10 executes a small workpiece rotation about the workpiece rotational axis R2 in one rotational direction (for example, in the clockwise direction) and in the opposite rotational direction (for example, counterclockwise). The double arrow FB therefore has a slight curvature in FIG. 2 to illustrate that it is a workpiece rotation about the workpiece rotational axis R2.

[0058] The workpiece rotation is executed with a predefined absolute value in one or in both rotational directions. The tooth gap 12 thus obtains an enlarged gap width. The gap width is greater here immediately after the classical cutting free than the tip width s.sub.a0 of the tool 100.

[0059] In the second method, the cutting free takes place upon reaching or after reaching the plunging final position while maintaining the first machine setting M1. Solely the crown gear workpiece 10 completes a workpiece rotation during the classical cutting free. Therefore, the symbol M1 is shown directly adjacent to the reference sign FB in FIG. 2B.

[0060] Carrying out correction machining KB now takes place, e.g., as illustrated in schematic form in FIG. 2A by the separate double arrow KB. The double arrow KB has a slight curvature in FIG. 2B, to illustrate that the correction machining KB takes place by the adjustment of the machine setting(s). The radius of curvature of this double arrow KB is oriented in the direction of the tool 100 (not shown), to thus represent the adjustment of the machine setting(s).

[0061] A flank angle error, for example, or also other errors of the tooth flanks of the tooth gap can be intentionally corrected by this type of the correction machining KB, which takes place while the tool 100 is located in the tooth gap of the crown gear workpiece 10. The adjustment of the machine setting is indicated in FIG. 2B in that, in addition to the reference sign KB, a second machine setting M2 and a third machine setting M3 are mentioned.

[0062] The tool 100 is drawn by a reverse-oriented movement AT out of the tooth gap after this correction machining KB has taken place by the adjustment of the machine settings. There is also a reversal point UP here.

[0063] If either the single-indexing or the continuous-indexing plunging methods are applied, the workpiece rotation which is used for the cutting free takes place with an angle absolute value which is significantly less than the indexing p of the crown gear workpiece 10 to be machined. In contrast to the single-indexing plunging method, during the continuous-indexing plunging method, the crown gear workpiece 10 rotates in a synchronized (coupled) manner in a specific ratio to the tool speed (depending on the tooth count and the cutter head number of threads). This synchronized movement is overlaid during the workpiece rotation with a phase shift of the rotational angle of the workpiece. This phase shift is also significantly less than the indexing p.

[0064] The values indicated hereafter each relate to the crown wheel which was used to design the crown gear 10. Therefore, all symbols are provided with a subscript P.

[0065] FIG. 3A shows a schematic top view of a section of a crown gear workpiece 10, on which a tooth gap 12 was pre-machined by conventional plunging in the single indexing method. Viewed from left to right, the illustration of the crown gear workpiece 10 comprises a tooth 11 (to be precise, it is the tooth head), a concave tooth flank 13.1, a tooth gap bottom having tooth base 12.1, a convex tooth flank 13.2, and a further tooth 11. The two tooth flanks 13.1, 13.2 are provided with a gray pattern to indicate that these flanks do not yet have the final form (the actual curve, or the actual topography, deviates from the setpoint curve, or the setpoint topography). They can have, for example, flank angle errors in the same direction, as already mentioned at the outset. To indicate that these are the tooth flanks after the plunging, the reference signs 13.1 and 13.2 are each provided with a superscript T. These are thus the tooth flanks 13.1.sup.T, 13.2.sup.T after the plunging.

[0066] A normal section through a tooth gap 12 is shown in schematic form in the upper part of FIG. 3A, which was pre-machined by plunging in the single indexing method. The section extends along section line A-A.

[0067] FIG. 3B shows the sectional illustration of FIG. 3A in an enlarged form. In addition to the instantaneous actual curve of the plunge-machined tooth flanks 13.1.sup.T, 13.2.sup.T (also called actual tooth flanks) the setpoint curve 13.1.sup.S,T, 13.2.sup.S,T (also called setpoint tooth flanks after the plunging) of the two flanks is illustrated by dashed lines. In the case shown, the actual tooth flanks 13.1.sup.T, 13.2.sup.T have a positive flank angle error FWF in relation to the setpoint tooth flanks 13.2.sup.S,T.

[0068] The flank angle error FWF is defined after the plunging as the difference between the setpoint curve 13.1.sup.S,T, 13.2.sup.S,T and the actual curve of the tooth flanks 13.1.sup.T, 13.2.sup.T. A positive flank angle error FWF is an angle error here in which the dotted line, which is used to illustrate the setpoint curve 13.1.sup.S,T, 13.2.sup.S,T in the direction of the tooth height, has a steeper slope than the actual curve of the tooth flanks 13.1.sup.T, 13.2.sup.T.

[0069] FIG. 3C shows the state after the cutting free by a workpiece rotation by the angle absolute value |?1| in a first rotational direction and by the angle absolute value |?2| in the opposing, second rotational direction. Since this conventional cutting free takes place using the same gear-cutting tool and only a workpiece rotation of the bevel gear workpiece 10 is performed, the flank angle error FWF is retained. Only the gap width e of the tooth gap 12 is enlarged by a small absolute value by the cutting free. The instantaneous actual curve of the tooth flanks is identified by a superscript F, as follows 13.1.sup.F, 13.2.sup.F. The setpoint curve 13.1.sup.S,F, 13.2.sup.S,F of the two flanks after the cutting free is illustrated by dashed lines.

[0070] The two short arrow tips identified with ?1 and ?2, which point in the clockwise direction and counterclockwise direction, respectively, illustrate the two workpiece rotations. The angle absolute value of the workpiece rotation may be equal in both rotational directions in some embodiments, i.e. |?1|=|?2|. The gap width e has been minimally expanded by the cutting free, which is hardly visible in comparison to FIGS. 3B and 3C.

[0071] The correction machining can be performed by changing the machine settings. The result after this correction machining is shown, for example, in FIG. 3D by the flank lines 13.1, 13.2. To indicate that the flank angle error FWF is equal to zero, or is nearly zero, the flank lines 13.1, 13.2 are shown in the form of interrupted straight lines in FIG. 3D.

[0072] It is to be noted that FIGS. 3A, 3B, 3C and 3D are of a schematic nature, and certain aspects have not been shown to scale, to make them visible at all. The tooth shape and the curve of the tooth base 12.1 are also illustrated.

[0073] The flank angle error FWF discussed here is an error which can be determined point by point on each tooth flank 13.1, 13.2 by measurement. Since these are flank angle errors FWF which have been induced by the plunging using the first machine setting M1, the flank angle error FWF along each of the tooth flanks 13.1 and 13.2 is constant in the flank longitudinal direction.

[0074] The illustration of FIGS. 3A, 3B, 3C and 3D can thus also be transferred to other positions along the tooth flanks 13.1, 13.2, since the flank angle error FWF is constant, as just mentioned.

[0075] The flank angle errors FWF, which can be remedied according to methods disclosed herein, are flank angle errors FWF, which are each measured in the vertical direction of the teeth 11.

[0076] The illustration of FIGS. 3A, 3B, 3C and 3D is based on a second method approach, in which the cutting free FB takes place separately from the correction machining KB, as shown in FIG. 2B.

[0077] However, the illustration of three steps in FIGS. 3B, 3C, and 3D was selected because this type of illustration enables the partial aspects to be illustrated and described and because this form of illustration is simpler and more comprehensible than a superimposed illustration of interlocking steps.

[0078] The first modified plunging method, in which the cutting free and the correction machining take place jointly, is illustrated in FIG. 2A.

[0079] What is described here may be applied to single-indexing methods, in which machining is performed tooth gap 12 by tooth gap 12 as shown in FIG. 2A or 2B, as well as to continuous-indexing methods, in which all gaps are subjected to the same plunging step followed by the correction machining method.

[0080] The adjustment of the machine setting relates here in some embodiments to the adjustment of at least one variable in addition to the workpiece pivot ?.

[0081] In a simplified special case, for example, in addition to the workpiece pivot ?, the cradle angle ? can also be changed in a first direction (referred to as second machine setting M2 here), to correct one concave tooth flank 13.1.sup.T (in the single-indexing method) or all concave tooth flanks 13.1.sup.T (in the continuous-indexing method). For the correction machining of one convex tooth flank 13.2.sup.T (in the single-indexing method) or all convex tooth flanks 13.2.sup.T (in the continuous-indexing method), the cradle angle ? is then changed in an opposing direction.

[0082] The differences of the three different machine settings M1, M2, M3 will be summarized once again on the basis of this simplified special case. In the first machine setting M1, the cradle angle is ?=?1 and during the plunging the depth position ? is changed, for example, from a starting depth position ?0 to ?1. The absolute value of this change is identified with ET in FIG. 1B.

[0083] The second machine setting M2 differs in the simplified special case from the first machine setting M1, for example, by way of a different cradle angle ?2??1 and by way of a workpiece pivot ??. The depth position ? remains, for example, unchanged, i.e., ?2=?1.

[0084] The third machine setting M3 differs in the simplified special case from the first and second machine settings M1 and M2, respectively, for example, by way of a different cradle angle ?3??2??1 and by way of a workpiece pivot +?. The depth position ? remains, for example, unchanged, i.e., ?3=?1=?2.

[0085] The transition of the cutter head gear-cutting tool 100 from the first machine setting M1 into the second machine setting M2 may take place while the cutting edges of the cutter head gear-cutting tool 100 are located in the tooth gap 12. Similarly, the transition of a grinding tool from the first machine setting M1 into the second machine setting M2 can also take place while the abrasive surfaces of the grinding tool are located in the tooth gap 12.

[0086] It is well known to a person skilled in the art in gear cutting that changing or adjusting a single variable of the machine setting of the gear cutting model can run to the adjustment of two or more than two variables in a real gear-cutting machine. This is because, inter alia, these are relative adjustments, which can often be executed more rapidly if, for example, the bevel gear workpiece 10 and the gear-cutting tool 100 are moved. Moreover, not every one of the available machines images the axes of the gear cutting model with 1:1 accuracy, but rather the axial constellations can sometimes be quite different.

[0087] The bevel gear workpiece 10 can be subjected to a measurement after the plunging and before carrying out the correction machining, to detect flank angle errors FWF and ascertain the size thereof.

[0088] However, one bevel gear workpiece 10 of a series of bevel gear workpieces can also be subjected to a measurement after the chip-removing machining in the plunging method, to then subsequently execute the correction machining in further bevel gear workpieces of the series of bevel gear workpieces.

[0089] As may be recognized by those of ordinary skill in the pertinent art based on the teachings herein, numerous changes and modifications may be made to the above-described and other embodiments without departing from the spirit and/or scope of the invention. Accordingly, this detailed description of embodiments is to be taken in an illustrative as opposed to a limiting sense.