Method for shaping periodic structures, in particular toothing and lift cams

Abstract

The invention relates to a method for shaping a periodic structure, in particular a toothing on a workpiece, in which a lifting mechanism lifts a shaping tool from the workpiece after a machining operation within a working stroke for a return stroke, characterized in that a rotational angle region of a lifting cam is functionally assigned to a circumferential cam contour region of a motor-driven rotating lifting cam of the lifting mechanism, which determines the engagement distance between the shaping tool and the workpiece in the working stroke portion of a stroke cycle, wherein the rotational angle region of the lifting cam passes again in the opposite rotational direction during the same stroke cycle.

Description

[0001] This invention relates to a method for forming teeth on periodic structures, particularly workpieces, wherein a lifting mechanism lifts the forming tool from the workpiece during the working stroke after a machining operation for a return stroke. The invention also relates to a lifting mechanism for a gear shaper.

[0002] This method for forming, particularly for forming teeth, is well known in the art. The basic principles of these methods are described, for example, in Thomas Bausch's "Innovative Gear Manufacturing," third edition, page 281 and onwards. The cutting speed during forming is generated by the basic vertical motion of the gear shaper cutter during the working stroke of the stroke cycle. Rotation and engagement are synchronized with the rotation of the tooth to be formed. However, to prevent cutting during the return stroke, the gear shaper cutter must be lifted (radially) from the workpiece tooth during the return stroke.

[0003] Despite their longer machining times, gear shaping methods, which compete with hobbing and cutting, are favored primarily in applications where hobbing is less suitable (e.g., internal gears) and in applications involving interference profiles, as both hobbing and cutting are less suitable for these applications due to their axial cross angles. However, sufficiently high stroke rates are desirable to keep machining times sufficiently short.

[0004] Regarding the lifting mechanism, a preferred technique is that of a rotary lifting cam. The desired profile of the path, consisting of the stroke and return stroke, is generated via the profile of a lifting cam that rotates continuously at a rotational speed corresponding to the stroke rate. In a typical design, for example as described in DE 10 2019 004 299 A1, a cam profile with a substantially constant diameter is provided for the working stroke, and a diameter-decreasing region is provided for the return stroke, followed by a diameter-increasing region to return to the diameter of the working stroke.

[0005] Additionally, other lifting mechanisms are known, which are based on linear motors and achieve lifting motion through a complex arrangement of flexible plates, as described, for example, in US 2005 / 0129474 A1. However, this variation does not appear to be the preferred method. In the lifting mechanism disclosed in DE 10 2006 052 474 A1, the specific implementation via a lifting cam is considered disadvantageous. Instead, a motor-driven crankshaft is taught, which is connected to the forming head via an intermediate lever. Lifting motion is controlled directly via an NC motor with digital control, starting from a rotational angle reference position corresponding to the working stroke. At least to the applicant's knowledge, this variation has not received significant market preference.

[0006] The problem to be solved by the present invention is to improve the type of method described at the beginning in terms of a satisfactory combination of machining speed and satisfactory machining accuracy.

[0007] This objective is achieved by means of a forming method of the type described at the beginning, the basic feature of which is that the rotational angular region of the lifting cam is functionally assigned to the circumferential cam profile region of the motor-driven lifting cam of the lifting mechanism, the circumferential cam profile region determining the engagement distance between the forming tool and the workpiece in the working stroke portion of the stroke cycle, wherein the rotational angular region of the lifting cam passes through a different time during the same stroke cycle—but in the opposite rotational direction.

[0008] This invention is based on the discovery that, although the engagement distance between the forming tool and the workpiece is controlled during the working stroke and the forming tool is lifted from the workpiece by the profile of the lifting cam (rotary lifting cam) during the lifting motion, the effect on the lifting motion can be achieved by driving the lifting cam with a rotational direction that changes at least twice, particularly exactly twice, during the stroke cycle (i.e., twice per double stroke), rather than by driving the lifting cam continuously in the same rotational direction as conventionally. In this case, the rotational angle zone corresponding to the cam profile area in the working stroke portion passes through at least twice, i.e., at least twice, in a rotational direction opposite to the first time. Preferably, the working stroke portion is allocated with a rotational angle zone of the lifting cam, which is preferably at least 5°, more preferably at least 10°, and particularly at least 20°, so that the lifting motion can begin from the lifting cam that has already accelerated to a specific angular velocity. Allocated rotational angle zones of 25° or greater, or even 30° or greater, are also possible.

[0009] Therefore, the rotational angular region (at least a portion thereof) within the working stroke can be used as an azimuth acceleration path. During lifting, the angular velocity of the lifting cam should preferably be at least 5 rpm, more preferably at least 20 rpm, and particularly at least 35 rpm. The expression "azimuth" in this context and hereinafter refers to the angular rotation (angle in the circumferential direction) of the rotating cam, such that the angular rotation of the rotating cam is therefore an angular acceleration path.

[0010] Of course, even during the return stroke, the angular zone of the lifting cam allocated to that return stroke passes through twice. In this regard, it is preferable to specify that there is a motion reversal point during the return stroke and another motion reversal point during the working stroke. This is beneficial for the efficient use of the stroke length used for engagement with the teeth. In principle, it is also kinematically conceivable to place two reversal points in the upward or downward movement of the forming head.

[0011] In one embodiment, the cam profile region may have a constant diameter, which is allocated to the rotation angle region passing through twice and determines the engagement distance between the forming tool and the workpiece. However, there is also a variation in which the cam profile region determining engagement may have a modulated diameter, for example, a variation in the tooth flank profile of the forming tooth.

[0012] Preferably, the teeth can be internal teeth, but the method is also applicable to external teeth. As will be explained in detail later, a single cam can be used to achieve both the lifting motion for forming internal teeth and the lifting motion for forming external teeth.

[0013] In a particularly preferred embodiment, the azimuth position (angular position of the reversing point) of the motion reversing point on the lifting cam during the return stroke is variablely adjustable, and particularly in the later stroke cycles of machining the workpiece, this azimuth position is adjusted to a position that results in a lower degree of lifting. Using this configuration, the advantage of the configuration according to the invention is that different degrees of lifting are easily achieved. Specifically, these different degrees of lifting can be achieved by the cam profile area assigned to the return stroke having a diameter (or radius) in at least some areas that increases during passage in one rotational direction and decreases accordingly during passage in another rotational direction—correspondingly forming a particularly linear ramp in one possible embodiment. The motion reversing point is further shifted upward or downward on this ramp by means of digital control of the cam rotation. In this way, for example, the teeth formed by multiple rotations can be machined in the return stroke with a first number of roughing strokes with a larger degree of lifting, and in the return stroke with a finishing stroke, or with a second number of finishing strokes with a smaller degree of lifting motion (regardless of the strategy used for the forward motion), thereby achieving higher machining accuracy. It is even conceivable to adjust the degree of ascent and descent in the return stroke of each stroke cycle (double stroke) individually and differently, for example as a function of the forward movement selected in the corresponding working stroke.

[0014] In a simple phase relationship, the reversing point of the stroke motion can be offset by π / 2 relative to the reversing point of the cam rotation. Then, the reversing point of the rotational motion on the working stroke side will substantially correspond to the center stroke position, and the reversing point on the return stroke side of the cam rotation will correspond to the center of the return stroke. Preferably, this phase relationship deviation does not exceed 5π / 12, preferably not more than π / 3, and especially not more than π / 4. However, in additional or alternative designs, compared to this basic layout with a π / 2 offset, the additional phase shift of the cam rotation in the direction of displacement of the reversing point of the cam rotation on the reverse stroke side in the end direction of the return stroke motion is adjustable, preferably at least π / 18, especially π / 9, especially at least π / 6, or even at least π / 4. This ensures a high level of displacement of the maximum lifting motion toward the upper end face of the forming teeth, where the risk of collision is a particular concern.

[0015] In another design option, the reversing point of the cam rotation on the working stroke side can also be shifted relative to the stroke in the direction of the lower end face of the forming teeth, in order to widen the azimuth acceleration path. However, depending on the width of the forming teeth (i.e., the tooth extension in the axial stroke direction) and especially in the case of relatively wide teeth, the reversing point of the cam rotation on the reverse side can also be shifted, wherein the same phase—the reversing point on the return stroke side shifted in the direction of the upper end face—is correspondingly deviated from the symmetry angular distance π, preferably not exceeding π / 2, more preferably not exceeding π / 3, more preferably not exceeding π / 4, and especially not exceeding π / 6. This increases the smoothness of the cam motion.

[0016] In principle, it is conceivable that the entire 360° (2π) rotation angle region of the cam is configured with a cam profile region for the working stroke and a cam profile region for the return stroke, and that, depending on its actuation, only a portion of the cam profile region is utilized according to the desired lifting motion. However, in another preferred configuration, it is specified that, in addition to these cam profile regions with associated rotation angle regions, there exists a remaining free rotation angle region, which can be used for one or more different cam profiles and can be applied accordingly.

[0017] For example, three rotational angular zones with associated cam profile areas can be provided: in a simple configuration, a zone with a constant radius for the working stroke used to form the external or internal gear, a zone for the return stroke used to form the external gear, and a zone for the return stroke used to form the internal gear. In this way, the cam does not need to be changed for machining changes from forming the external gear to forming the internal gear. According to the above description, the possibility of adjusting the degree of rise for forming the internal gear and for forming the external gear is maintained, particularly the possibility of continuous adjustment. Of course, for this example, separate angular zones for the working strokes used for internal gear machining and external gear machining could also be provided. However, a combination of the two methods is possible regarding the working stroke.

[0018] If the three segments described above are further compressed compared to the example above, for example, to a total extension of 180° (π), it is also conceivable to apply another cam profile on the same cam. This other cam profile allows for radial variations within the working stroke to modify the tooth flank profile of the forming teeth, such as width convexity or taper. These designs can also be combined, for example, by using a cam profile area modified to produce both the machining of internal teeth and the machining of external teeth, by providing a corresponding profile for the return stroke on one side or the other.

[0019] In this respect, it can therefore be specified that the third-party angular region (corner region) is also shaped in some regions for use in lifting processes, but with different profiles, and particularly for lifting processes of another workpiece type, another workpiece, or earlier or later stroke cycles of the same workpiece, and / or for working strokes with tooth flank modifications that are at least partially modified via these profiles and have shaped teeth.

[0020] If the angular region traversed by the lifting cam in its stroke cycle is considered a function of time, then a periodic function related to the frequency of the stroke cycle is provided.

[0021] The time derivative of the periodic function, and especially the periodic function itself, is particularly preferably sinusoidal or modulated sine waves. That is, the first-order sine wave is dominant, and / or there are at least two changes within one period from one curvature direction to another; there are at least two continuous regions, one above the centerline and the other below the centerline, and such centerlines intersect at least twice within the period. In the absence of possible tooth surface modifications, this function can also specifically correspond to a precise sine radius, wherein, as explained above, three parameters—amplitude, phase shift, and zero-point offset for amplitude—can be used to actuate the cam rotation to adjust the commutation point of the cam rotation relative to the phase of the stroke motion. Furthermore, it is stipulated that the lifting motion and the change of cam direction are performed with the smallest possible impact. For this purpose, it is preferably stipulated that the periodic function (and especially its derivative) is specifically differentially distinct twice continuously.

[0022] In another preferred configuration, the quotient of the maximum amplitude of the angular velocity (the time derivative of the rotation angle of the lifting cam) and the cycle time is specified to be less than 24 rpm / s, preferably less than 16 rpm / s, and particularly less than 8 rpm / s. In this way, excessive acceleration that could negatively affect machining quality will not occur.

[0023] In another preferred configuration, the stroke frequency processed, measured in strokes per minute, is specified to be greater than 50, preferably 150, more preferably 200, and particularly greater than 250. Due to the aforementioned available azimuth acceleration paths, reliable lifting motion is achieved, and even at high stroke rates, return strokes are prevented from passing despite the reverse direction of cam rotation. It should be understood that significantly higher values, such as 400 or higher, 800 or higher, or even 1200 or higher, can be used.

[0024] In another preferred configuration, the periodic function of the angle of the lifting cam as a function of time includes modifications for generating the tooth flank profile of the formed tooth, for example, also in the form of (at least) four curvature changes within one cycle. In this way, modulation, for example, a sine function can be provided to compensate for the non-constant stroke speed during the working stroke when generating the width convexity desired only at the center of the tooth.

[0025] In a preferred structural design for implementing this method, the forming head is mounted to pivot about an axis, and lifting motion is performed by pivoting the forming head. Furthermore, the lifting mechanism may have a preloaded pressure roller arranged between the lifting cam and the pivotable forming head area.

[0026] The present invention also relates to a control program with control instructions that, when executed on the control device of the gear shaper, controls the gear shaper to perform the method according to any of the foregoing aspects. Furthermore, the present invention provides a rotary lifting cam for the lifting mechanism of a gear shaper, the rotary lifting cam having a first circumferential cam profile area and a second circumferential cam profile area, the first circumferential cam profile area for adjusting the relative distance between the gear shaper cutter and the workpiece in a first operating mode, and the second circumferential cam profile area for adjusting this relative position in a second operating mode, the second operating mode having a different relative motion path compared to the first operating mode. As explained above, these different cam profile areas implemented on a single lifting cam may include, for example, lifting movements during forming of the internal teeth in the opposite direction to the forming of the external teeth, modified working strokes, for example, modifications to the forming teeth, particularly modifications to the tooth flank profile, such as convexity, end taper or conicity, or combinations thereof.

[0027] Finally, the present invention also provides a gear hobbing machine having a control program for performing this method and / or having such a lifting cam. The digitally controlled rotary motor for rotating the rotary cam is preferably, for example, a synchronous motor with a coupling or an assembled synchronous motor, as commercially available from the relevant manufacturer.

[0028] Further features, details, and advantages of the invention will become apparent from the following description with reference to the accompanying drawings, wherein:

[0029] Figure 1 This is an explanatory diagram of the cam motion curve.

[0030] Figure 2 This is an illustration of the cam angle as a function of time.

[0031] Figure 3 It is an illustration of two lifting and lowering movements.

[0032] Figure 4 This is a schematic diagram of a forming head with a cam.

[0033] Figure 5 This is a schematic diagram of a cam with different cam segments.

[0034] Figure 6 yes Figure 5 A diagram illustrating the lifting and lowering motion of the cam section VI.

[0035] Figure 7 yes Figure 5 A diagram illustrating the rising and falling motion of zone VII.

[0036] Figure 8 yes Figure 5A diagram illustrating the rising and falling motion of zone VIII, and

[0037] Figure 9 yes Figure 5 The diagram illustrates the rising and falling motion of area IX.

[0038] Figure 4 A forming head 100 is schematically shown, carrying a gear shaping cutter 40 to perform a gear shaping machining process for generating teeth 55 on a workpiece 50. For this purpose, the forming head performs a stroke movement along a stroke axis indicated by a double arrow with the reference numeral Z. This is achieved in a known manner by means of a crank drive (not shown) having a forming mandrel axis (A axis), which is a continuously rotating axis of rotation.

[0039] exist Figure 4 The suspension of the shaped head, which is not shown in the figure, is capable of lifting motion (indicated by a double arrow with reference numeral xn) to prevent return stroke collision. The degree of lifting is based on the diameter (and / or radius) of the irregular cam 10. Figure 4 The irregularly shaped cam contacts the preloaded pressure roller 20 at the 3 o'clock position, where... Figure 4 Only one area of ​​the cam is shown. Therefore, the structure of the forming head can be as described in DE 10 2019 004 429. Figure 3 The document concerning that basic design is incorporated herein by reference.

[0040] exist Figure 4 In this document, the direction of rotation of the continuously rotating cam used in the prior art references is depicted as dashed arrow 11. This cam controls the lifting motion synchronously with the stroke motion. The cam rotation, along with other machine axes, is controlled digitally; the controller used here... Figure 4 The figure is indicated by reference numeral 99.

[0041] In contrast, the cam rotational motion used in the method according to the invention is represented by a rotating double arrow 12. Therefore, the cam rotation is not continuous in the same direction of rotation, but changes direction of rotation during the (double) stroke, and passes through the angular region more than once in the (double) stroke (exactly twice in this exemplary embodiment), and in particular, the rotational direction of the rotating cam is different for each channel.

[0042] The representation that extends over slightly more than three complete double passes over time (such as...) Figure 2In the representation, this is evident from the example with the thick solid line curve Mt1, compared to the thin dashed curve Mt0 of the prior art. The zigzag depiction of curve Mt0 in the prior art is due to the fact that after the cam 10 has fully rotated, the angle is redefined starting from the zero-crossing point corresponding to the 360° position. In contrast, for curve Mt1 of the first operation, it passes through only one angular region of approximately 100°, and for the example shown, it is a function of the time period with the period duration corresponding to the period of the double stroke, and in the form of a sine curve in this exemplary embodiment.

[0043] Figure 1 Showing the corresponding Figure 2 The motion of curve Mt1 is shown in the figure, where the cam radius is plotted as a function of the cam angle α2. The dashed curve Dα2 represents the profile of the cam in the rotation angle region under discussion. This dashed curve has a region Dc with a constant radius and a region Dv with a radius that decreases with the cam angle α2. To illustrate and identify the different rotation directions, curve Mα21 is shown in... Figure 2 The curve Mt1 is depicted above the cam curve Dα2, corresponding to the motion Mt1 in one direction of rotation below and another direction of rotation above. Of course, in reality, curve Mα21 lies on the cam curve Dα2. Figure 2 and Figure 1 The influence of paths Mt1 and Mα21 on the lifting motion can be seen in Figure 3 The diagram best illustrates this, and specifically, instantaneous states A, B, C, and D are also present. Figure 1 and Figure 2 As shown in the image.

[0044] Instantaneous case A describes the start of the motion as the working stroke—without any lifting or lowering movement—which ends at point C. During the working stroke, the radial distance between the gear shaper 40 and the workpiece 50 should remain constant during the operation (assuming no modification to the width of the convex surface, or the tapered or other tooth profile is expected). Therefore, Figure 2 The curve Mα21 passes through the region Dc of constant cam radius, specifically transitioning from the variable radius region Dv to the constant radius region Dc via instantaneous condition B, in which the cam's rotational speed decreases to zero after deceleration and then increases again in the opposite rotational direction. During the working stroke (without modification), the position of a given point on curve Mα21 plays a secondary role. The specification of the angular velocity ω2 (=dα2 / dt) is therefore completely variable, and the "reversal point" B in region Dc (where ω2=0) need not be located as shown in the diagram. Figure 3 The center of the shown route. More precisely, this reversing point can be determined relative to... Figure 2 The phase shift is located at a position different from the center position in the axial travel direction Z.

[0045] Figure 1 The angular region [α2B; α2C] between instantaneous states B and C can be used as an acceleration path, allowing the lifting motion starting from instantaneous state C to occur when the cam's angular velocity may already have a relatively high value, especially close to its maximum value. However, it should also be understood in this paper that, with the aid of digital control of axis α2, the cam's maximum speed can also be relative to... Figure 3 The angular velocity ω2 changes due to the rising and falling motion. For example, the angular velocity ω2 will not need to decrease from the moment the rising and falling motion begins. More precisely, the angular velocity may also briefly rise, then fall, and rise again from instantaneous point D (another "reversal point" relative to the direction of rotation of the angular velocity). Figure 3 In China, according to Figure 1 The reversing point D, corresponding to the maximum lifting motion of the selected cam profile Dα2, is also plotted at the center of the axial motion z; however, this can also be shifted in the direction, for example, where the return stroke motion Mxv1 ends. As the cam rotates from the reversing point D to the transition zone Dv to Dc, in Figure 1 In instantaneous scenario A, the ascent and descent motion ends, and the starting point of the example is reached again.

[0046] exist Figure 3 The diagram also shows another lifting motion Mx2, which, during the working stroke (Mxc2), corresponds to the lifting motion Mx1 (with the return stroke Mxv1) just discussed; however, during the return stroke, as can be seen from the dashed motion path, it lifts and lowers by a relatively large degree. This is achieved by rotating the cam (cam angle α2) beyond the specified range using a digital controller 99. Figure 1 The previously described motion Mα21's "reversal point" D region, and therefore, instantaneously, between C and A (via D), in one direction and then in another rotational direction, passes through the larger angular region of region Dv with a variable cam radius. Thus, from Figure 2 As can be seen, the larger the amplitude of curve Mt2 relative to curve Mt1, the greater the vertical motion. Figure 1 In the Mα22 path, a larger angular region is also traversed within the constant cam radius region Dc. However, it should be understood again in this paper that the positioning of the "reversal point" B along region Dc has no effect on the radial distance between the gear shaper 40 and the workpiece 50, and therefore can in principle be changed (corresponding to...). Figure 2 The curve in the figure is shifted along the vertical axis and stretched / compressed.

[0047] Therefore, different lifting paths can be achieved using the same cam, that is, without changing the cam, and lifting motion can also be achieved after passing through the angular acceleration segment.

[0048] The entire periphery of the lifting cam does not require lifting movement; Figure 1 and Figure 2 The angle regions shown for illustrative purposes (approximately 100° for curves / paths Mt1 / Mα21 and approximately 200° for Mt2 / Mα22) can, of course, be further reduced. In another aspect of the invention, lifting cams with different profile regions can thus be realized for different lifting movements and / or adjustments to the working stroke (beyond the amplitude adjustment described above).

[0049] The following will refer to Figure 5 To illustrate this, the figure shows the outlines of the cams in different segments 1 through 6 in a greatly magnified view. In the illustration using the time on a clock as the angular position, the figure shows the first segment 1 between the 0 o'clock position and the 2 o'clock position, the second segment 2 between the 2 o'clock position and the 4 o'clock position, the third segment 3 between the 4 o'clock position and the 6 o'clock position, the fourth segment 4 between the 6 o'clock position and the 8 o'clock position, the fifth segment 5 between the 8 o'clock position and the 10 o'clock position, and the sixth segment 6 between the 10 o'clock position and the 12 (0) o'clock position.

[0050] Segment 2 has a constant radius and corresponds to Figure 1 The region Dc. Segment 1 has a radius that decreases in the counterclockwise direction and corresponds to Figure 1 In the Dv area. Figure 5 The two segments 1 and 2, which are part of the VI combination, can be used to form, for example... Figure 6 The external teeth shown. Generated according to... Figure 3 The lifting motion is of type Mx1 or Mx2, which can be further controlled digitally (e.g., according to...). Figure 2 The amplitude can be adjusted to set different degrees of rise and fall. See the above reference. Figure 3 As explained, these degrees of elevation can be continuously set by positioning the reversing point D.

[0051] However, segment 2 can also be used to shape the internal gear, and the radial lifting motion of this internal gear must occur in the opposite direction to the direction of external gear shaping. For this purpose, segment 3 is provided, which is connected to segment 2 on the other side of segment 1 and has a region that rises clockwise with a cam radius. Figure 5 The regions of segments 2 and 3, denoted by VII, can therefore be used to shape the internal teeth. The corresponding lifting and lowering movements are as follows: Figure 7 As shown. Also in this article, refer to Figures 1 to 3 The described changes in lifting motion can be specifically adjusted regarding the degree of lifting because, in addition to the cam traversing the angular zone twice (with different directions of rotation) as determined by digital control of the angular velocity, there are further degrees of freedom regarding the speed of these path traversals. Figure 2(The change in the shape of curve Mt1 in the text).

[0052] like Figure 5 As shown, the remaining angular regions of the cams with segments 4, 5, and 6 can be used for this purpose to achieve topological modification of the tooth geometry of workpiece 50. This is initially illustrated using an example of a tooth flank profile convexity or a width convexity. Segment 6 produces a cam profile that is mirror-symmetric to segment 1, i.e., a region where the cam radius increases counterclockwise. This cam profile is adjacent to segment 5; however, this segment does not have a constant radius. This segment is designed such that the radius initially derived from segment 6 first decreases during further rotation and then increases again approximately from the midpoint of the angular region assigned to segment 5. Also in this document, for illustrative purposes, a representation of the deviation of the constant diameter is shown at a greatly magnified scale (indicated by double dashed lines). Figure 5 Segments 5 and 6, denoted by IX, are used together to form the external tooth with a modified tooth profile featuring a wide convex surface. The associated lifting motion is... Figure 9 As shown in the image. (and) Figure 6 In contrast, relatively small convex lifting and lowering movements can also be seen during the working stroke.

[0053] Finally, segment 4, designed to be a mirror image of segment 3, can be used with segment 5, such as... Figure 5 As shown in VIII, this is used for rolling internal teeth with a wide convex surface. The associated lifting motion is... Figure 8 As shown in the image.

[0054] For this exemplary embodiment of the convex surface, the degree of rise and fall of the lifting motion during the return stroke can continue via segment 4 ( Figure 8 ), fragment 6 ( Figure 9 ), fragment 3 ( Figure 7 ) and fragment 1 ( Figure 6 The corner area is set in the ) )

[0055] With the help of Figures 1 to 3 The different lifting movements shown, with varying degrees of elevation, can be used not only to shape the teeth of different workpieces, but also to shape the teeth of the same workpiece, for example, by using... Figure 3 The lifting path in the return stroke Mxv2 serves as the return stroke of the roughing stroke, wherein a smaller lifting motion can be set in the return stroke after one or more finishing passes of one or more finishing strokes by moving the reversing point and / or instantaneous case D in the direction of the zone Dc of a constant cam radius. It should be understood that alternatively, or other tooth profile modifications not explicitly shown (such as taper or end taper) besides the convex surface, can be achieved by modifying the circumferential zone of the rotary cam.

[0056] As can be seen from the above detailed description of the present invention, the flexibility of the forming process is further increased, and the downtime that would otherwise have been caused by removing and installing another cam is also reduced.

[0057] Furthermore, the present invention is not limited to the details shown in the foregoing description. Rather, the various features described above and in the following claims, individually or in combination, are essential for carrying out different embodiments of the invention.

Claims

1. A method for forming a periodic structure, said periodic structure being a tooth (55) on a workpiece (50), wherein a lifting mechanism lifts a forming tool (40) from the workpiece within a working stroke (Mxc1) after a machining operation for a return stroke (Mxv1). Its features The rotation angle zone ([α2B; α2C]) of the lifting cam is functionally assigned to the circumferential cam profile zone (DcF; 2) of the motor-driven rotating lifting cam (10) of the lifting mechanism, which defines the engagement distance between the forming tool and the workpiece in the working stroke portion of the stroke cycle, wherein the rotation angle zone of the lifting cam passes again in the opposite rotation direction during the same stroke cycle.

2. The method of claim 1, wherein the rotation angle region in the working stroke portion is used as an azimuth acceleration path in at least some areas.

3. The method according to claim 1 or 2, comprising the motion reversal point (D) in the return stroke and / or the motion reversal point (B) in the working stroke.

4. The method according to claim 3, wherein the azimuth position of the motion reversal point on the return stroke side of the lifting cam can be variably adjusted.

5. The method of claim 4, wherein in a later stroke cycle of machining the workpiece, the azimuth position is adjusted to a position that causes a lower degree of rise and fall.

6. The method of claim 4, wherein the azimuth position of the motion reversal point on the return stroke side is phase-shifted relative to the axial center of the return stroke.

7. The method of claim 6, wherein the azimuth position of the motion reversal point on the return stroke side is phase-shifted relative to the axial center of the return stroke by at least π / 18.

8. The method of claim 6, wherein the azimuth position of the motion reversal point on the return stroke side is phase-shifted by at least π / 12 relative to the axial center of the return stroke, and phase-shifted in the direction of the end of the return stroke.

9. The method of claim 6, wherein the azimuth position of the motion reversal point on the return stroke side is phased relative to the axial center of the return stroke and phased in the direction of the end of the return stroke.

10. The method according to claim 1 or 2, wherein the circumferential cam profile region of the lifting cam assigned to the return stroke and determining the lifting motion, together with the cam profile region assigned to the working stroke, has a total azimuth extension of less than 360°, and therefore does not cover the third azimuth region.

11. The method according to claim 1 or 2, wherein the circumferential cam profile region of the lifting cam assigned to the return stroke and determining the lifting motion, together with the cam profile region assigned to the working stroke, has a total azimuth extension of less than 240°, and therefore does not cover the third azimuth region.

12. The method of claim 10, wherein the third azimuth region is also shaped in some regions for use in the lifting process, but has a different profile.

13. The method of claim 12, wherein the third-party azimuth region is shaped for the lifting process of an earlier or later stroke cycle of another workpiece type or the same workpiece, and / or for a tooth flank modified work stroke with a shaped periodic structure at least partially modified via the profile.

14. The method of claim 12, wherein the third-party azimuth region is shaped for the lifting process of an earlier or later stroke cycle of another workpiece or the same workpiece, and / or for a tooth flank modification work stroke with a shaped periodic structure modified at least partially via the profile.

15. The method according to claim 1 or 2, wherein the angle region traversed by the lifting cam in the stroke cycle is a periodic function, the periodic function being a function of time and related to the frequency of the stroke cycle.

16. The method of claim 15, wherein the time derivative of the periodic function is sinusoidal or a modulated sine wave.

17. The method of claim 16, wherein the periodic function is sinusoidal or a modulated sine wave.

18. The method according to claim 1 or 2, wherein the quotient of the maximum amplitude of the angular velocity and the cycle time measured in rpm / s is less than 24.

19. The method according to claim 1 or 2, wherein the quotient of the maximum amplitude of the angular velocity and the cycle time measured in rpm / s is less than 16.

20. The method according to claim 1 or 2, wherein the quotient of the maximum amplitude of the angular velocity and the cycle time measured in rpm / s is less than 8.

21. The method according to claim 1 or 2, wherein the travel rate in travels per minute is greater than 50.

22. The method of claim 1 or 2, wherein the travel rate in travels per minute is greater than 150.

23. The method of claim 1 or 2, wherein the travel rate in travels per minute is greater than 200.

24. The method according to claim 1 or 2, wherein the periodic function of the angle of the lifting cam as a function of time includes four changes in the direction of curvature within one period.

25. The method of claim 1 or 2, wherein the forming head is pivotally mounted about an axis, and the lifting movement is achieved by pivoting the forming head.

26. The method of claim 25, wherein the lifting mechanism has a preloaded pressure roller disposed between the lifting cam and the forming head.

27. A computer-readable storage medium storing thereon a control program including control instructions, characterized in that, When the control program is executed in the control device (99) of the gear hobbing machine, it causes the gear hobbing machine to perform the method according to any one of claims 1 to 26.

28. A rotating lifting cam (10) of a lifting mechanism for a gear shaper, the rotating lifting cam having a first circumferential cam profile area (1, 2) and a second circumferential cam profile area (2, 3; 1, 6), the first circumferential cam profile area being used to adjust the relative distance between the gear shaper cutter and the forming workpiece in a first operating mode, and the second circumferential cam profile area being used to adjust this relative position in a second operating mode, the second operating mode having a different relative motion path compared to the first operating mode. in, The rotation angle region ([α2B; α2C]) of the lifting cam (10) is functionally assigned to the first circumferential cam profile region of the lifting cam (10), wherein the rotation angle region ([α2B; α2C]) of the lifting cam (10) passes through again in the opposite rotation direction during the same stroke cycle.

29. The rotating lifting cam according to claim 28, the rotating lifting cam comprising at least one cam profile region (5), the at least one cam profile region being modified to generate a tooth flank profile modification and having a non-constant radius.

30. A gear hobbing machine, the gear hobbing machine comprising a controller having a computer-readable storage medium according to claim 27 and configured to perform the method according to any one of claims 1 to 26.

31. The gear hobbing machine as described in claim 30, characterized in that... It has a rotating lifting cam as described in claim 28 or 29.

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