Abstract
A machine tool for machining pre-toothed workpieces has a workpiece carrier, a workpiece spindle with a workpiece spindle housing and a workpiece spindle shaft. The machine tool has a meshing sensor, a calibration piece, and a sensor controller which is designed to perform the following procedure: Moving the meshing sensor relative to the workpiece spindle into a calibration position in which the meshing sensor is located at the calibration piece 10; determining a response behavior of the meshing sensor by the sensor controller moving the meshing sensor relative to the calibration piece and meanwhile receiving sensor calibration signals of the meshing sensor, and moving the meshing sensor into a workpiece measuring position in which the meshing sensor is located at the workpiece, the workpiece measuring position depending on the determined response behavior.
Claims
1. A machine tool for machining pre-toothed workpieces, comprising: a workpiece carrier; workpiece spindle arranged on the workpiece carrier and defining a workpiece spindle axis, the workpiece spindle having a workpiece spindle housing and a workpiece spindle shaft rotatable in the workpiece spindle housing about the workpiece spindle axis for rotationally driving a pre-toothed workpiece to be machined; a meshing sensor configured to detect a phase position of teeth of the workpiece when the workpiece rotates about the workpiece spindle axis, wherein the machine tool further comprises: a calibration piece located at a defined calibration point relative to the workpiece spindle; and a sensor controller configured to carry out the following method: moving the meshing sensor relative to the workpiece spindle to a calibration position in which the meshing sensor is located at the calibration piece; determining a response behavior of the meshing sensor by the sensor controller moving the meshing sensor relative to the calibration piece while receiving sensor calibration signals of the meshing sensor, and moving the meshing sensor to a workpiece measuring position in which the meshing sensor is located at the workpiece, wherein the workpiece measuring position depends on the determined response behavior.
2. The machine tool according to claim 1, wherein moving the meshing sensor relative to the calibration piece includes at least one of: movements in an axial direction, in a radial direction, or in a tangential direction with respect to the workpiece spindle.
3. The machine tool according to claim 1, wherein the calibration piece is arranged on the workpiece carrier.
4. The machine tool according to claim 1, wherein the calibration piece is arranged on a stationary part of the workpiece spindle.
5. The machine tool according to claim 1, wherein the calibration piece is arranged on a rotatable part of the workpiece spindle.
6. The machine tool according to claim 1, wherein the workpiece spindle has a clamping means for clamping a workpiece on the workpiece spindle shaft, and wherein the calibration piece is arranged on the clamping means.
7. The machine tool according to claim 6, wherein the calibration piece is configured such that it can be detachably fastened to the clamping means.
8. The machine tool according to claim 7, wherein the calibration piece is configured such that it is attachable to and removable from the clamping means by an automatic workpiece loading device.
9. The machine tool according to claim 1, wherein the calibration piece has a substantially cuboid base body.
10. The machine tool according to claim 9, wherein the base body of the calibration piece has a first groove.
11. The machine tool according to claim 10, wherein the calibration piece is arranged in the machine tool such that the first groove in the base body of the calibration piece runs perpendicular to the workpiece spindle axis.
12. The machine tool according to claim 10, wherein the base body of the calibration piece has a second groove, which runs at an angle to the first groove and opens into the first groove.
13. The machine tool according to claim 1, wherein the calibration piece has a cuboid projection extending radially from a surface of a portion of the workpiece spindle, wherein the cuboid projection is flanked by two orientation areas, and wherein the flanking orientation areas are arranged on both sides of the projection with respect to a tangential direction.
14. The machine tool according to claim 1, wherein the calibration piece has a cylindrical base body.
15. The machine tool according to claim 1, wherein the calibration piece has a spherical base body or a dome-shaped base body.
16. The machine tool according to claim 1, wherein the calibration piece is disc-shaped and has an outer profile with at least one tooth structure.
17. The machine tool according to claim 16, wherein the calibration piece is a workpiece to be machined.
18. The machine tool according to claim 1, wherein the machine tool comprises a tactile sensor, wherein the tactile sensor is adapted to measure the calibration piece to obtain a defined calibration point.
19. The machine tool according to claim 1, wherein the machine tool has a tool carrier on which a tool spindle for rotationally driving a machining tool is arranged, and wherein the meshing sensor is arranged on the tool carrier.
20. The machine tool according to claim 1, wherein the sensor controller is configured to cause the movement of the meshing sensor relative to the workpiece spindle by movements of the tool carrier relative to the workpiece spindle.
21. The machine tool according to claim 1, wherein the machine tool comprises a sensor positioning device for positioning the meshing sensor, which is arranged on the tool carrier and is movable together with the tool carrier relative to the workpiece spindle, wherein the sensor positioning device is configured to move the meshing sensor relative to the tool carrier, and wherein the sensor controller is configured to effect the movement of the meshing sensor relative to the workpiece spindle by at least one of: movements of the tool carrier relative to the workpiece spindle or by movements of the sensor positioning device relative to the tool carrier.
22. The machine tool according to claim 21, wherein the sensor positioning device comprises a sensor positioning arm which is movable relative to the tool carrier.
23. The machine tool according to claim 21, wherein the sensor positioning device comprises a sensor holder for receiving a sensor carrier, wherein the sensor carrier comprises a stop element, wherein the meshing sensor has a meshing sensor surface, and wherein the meshing sensor is mounted in the sensor carrier such, that the meshing sensor surface is at a defined distance from the stop element.
24. The machine tool according to claim 1, wherein the meshing sensor is an inductive meshing sensor, and wherein at least one of: the calibration piece consists of an electrically conductive material or has an electrically conductive surface.
25. The machine tool according to claim 1, wherein the meshing sensor is a capacitive meshing sensor, and wherein at least one of: the calibration piece consists of a dielectric material or has a surface made of a dielectric material.
26. The machine tool according to claim 1, wherein the meshing sensor is configured to output a switching signal, wherein the meshing sensor has a sensor-specific switching region, and wherein the sensor-specific switching region defines a fictitious sensor axis.
27. The machine tool according to claim 26, wherein the calibration point of the calibration piece in a coordinate system of the workpiece carrier is known, wherein the sensor controller is configured to determine the fictitious sensor axis by determining the response behavior of the meshing sensor on the calibration piece, wherein the sensor controller is further configured to calculate the workpiece measuring position from the known calibration point of the calibration piece, a predefined measuring axis and the determined fictitious sensor axis in such a way that the determined fictitious sensor axis coincides with the predefined measuring axis when the meshing sensor is in the calculated workpiece measuring position.
28. The machine tool according to claim 26, wherein the sensor controller for determining the response behavior of the meshing sensor is configured to determine a peak switching point of the switching region in a coordinate system of the workpiece carrier by moving the meshing sensor in the normal direction towards an end face of the calibration piece.
29. The machine tool according to claim 27, wherein the calibration point of the calibration piece and the predefined measuring axis are stored in a memory of the sensor controller and the method is carried out automatically.
30. The machine tool according to claim 4, wherein the calibration piece is arranged on the workpiece spindle housing.
31. The machine tool according to claim 10, wherein the first groove has a rectangular or trapezoidal cross-section.
32. The machine tool according to claim 12, wherein the second groove has at least one of: a rectangular or trapezoidal cross-section or runs perpendicular to the first groove.
33. The machine tool according to claim 16, wherein the tooth structure is a calibration tooth.
34. The machine tool according to claim 22, wherein the sensor positioning arm is linearly displaceable relative to the tool carrier.
35. The machine tool according to claim 24, wherein the calibration piece consists of steel or cast steel or aluminum.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,
[0059] FIG. 1a, 1b show in perspective view an embodiment of a machine tool for machining pre-toothed workpieces according to the present invention;
[0060] FIG. 2a-2d show in perspective view five different embodiments of a calibration piece according to the present invention;
[0061] FIG. 2e shows in perspective view a machine tool according to the present invention with a sixth embodiment of the calibration piece;
[0062] FIG. 2f shows an enlarged perspective view of the sixth embodiment of the calibration piece of FIG. 2e;
[0063] FIG. 2g shows a side view of a machine tool according to the present invention with a seventh embodiment of the calibration piece;
[0064] FIG. 2h shows in an enlarged side view the seventh embodiment of the calibration piece of FIG. 2g;
[0065] FIG. 3a, 3b show a preferred arrangement of a calibration piece in a machine tool according to the present invention;
[0066] FIG. 3c shows a sensor holder for holding the meshing sensor;
[0067] FIG. 4a-4d show in a schematic (not to scale) manner, a method for calibrating a meshing sensor according to the present invention;
[0068] FIG. 5 shows a flowchart illustrating a method according to one embodiment of the present invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0069] FIGS. 1a and 1b show a perspective view of an embodiment of a machine tool 2 for machining pre-toothed workpieces, with FIG. 1b showing an enlargement of the section E framed in FIG. 1a. In particular, the embodiment shown here is a machine tool for the rolling machining of rotary parts with groove-shaped profiles. Such a machine tool is described in document WO2021008915A1, the disclosure of which is incorporated herein by reference in its entirety. The machine tool 2 has a workpiece carrier 20, a workpiece spindle 21 arranged on the workpiece carrier 20 and defining a workpiece spindle axis A, the workpiece spindle 21 having a workpiece spindle housing 211 and a workpiece spindle shaft 212 rotatable in the workpiece spindle housing 211 about the workpiece spindle axis A for rotationally driving a pre-toothed workpiece to be machined, and a clamping means 22, the clamping means 22 being configured to receive a workpiece to be machined. A Cartesian coordinate system K.sub.M referenced to the workpiece carrier 20 with an X.sub.M direction, a Y.sub.M direction and a Z.sub.M direction is drawn in FIG. 1b, here as an example with origin on the workpiece spindle axis A. In the embodiment example shown here, the workpiece carrier 20 is a workpiece slide that can be moved in the Y.sub.M direction. The machine tool 2 shown here also has a sensor positioning device 25, which is arranged on a tool carrier 24, wherein a tool spindle 241 for rotationally driving a machining tool is arranged on the tool carrier 24. The sensor positioning device 25 is movable together with the tool carrier 24 in the X.sub.M direction and in the Z.sub.M direction and has a sensor positioning arm 251 which is linearly displaceable in a Y.sub.M/Z.sub.M plane and in which the meshing sensor 1 is arranged. Here, the meshing sensor 1 is aligned antiparallel to the Y.sub.M direction. In FIGS. 1a and 1b, different embodiments of a calibration piece 10 are arranged in the same machine tool 2 for illustrative purposes. In practice, however, it is usually sufficient if the machine tool has only one of these embodiments of the calibration piece 10. As can be seen from FIG. 1b, the various embodiments are arranged in the machine tool in such a way that the meshing sensor 1 can be moved along the calibration piece 10 by means of the sensor positioning device 25 in order to determine its response behavior, whereby the meshing sensor always remains aligned antiparallel to the Y.sub.M direction during the movements 1 here. Furthermore, in order to achieve a movement of the calibration piece 10 relative to the meshing sensor 1 in the Y.sub.M direction, the workpiece carrier 20 can also be moved in the machine tool 2 shown here. Also shown is a scanning means 30 arranged on the tool carrier 24, which can be used to determine the calibration point C.sub.M of the calibration piece 10 in the coordinate system K.sub.M of the machine tool 2.
[0070] FIGS. 2a-d show enlarged versions of the calibration piece 10 shown in FIGS. 1a and 1b.
[0071] In the image section D.sub.1 of FIG. 1b shown in FIG. 2a, two embodiments of the calibration piece 10 can be seen. Both embodiments are arranged on the workpiece spindle housing 211. The first embodiment shown in the image detail in a front plane has a cuboid base body, wherein the base body has a first groove 11 with a rectangular cross-section, wherein the first groove 11 extends in the X.sub.M direction. The second embodiment shown in a rear plane in the image detail protrudes from a beveled surface of the workpiece spindle housing 211 and also has a first groove 11 extending in the X.sub.M direction with a rectangular cross-section. As can be seen in FIG. 1b, both of these embodiments are arranged on the workpiece spindle housing such that the groove 11 extends in a tangential direction with respect to the workpiece spindle 21. In order to determine the response behavior of the meshing sensor 1, the meshing sensor 1 on a side of the calibration piece 10 having the groove 11 can be moved in the tangential direction along the groove 11 and/or in the Z.sub.M direction (which corresponds to an axial direction with respect to the workpiece spindle 21) and/or in the Y.sub.M direction (which corresponds to a radial direction with respect to the workpiece spindle 21).
[0072] In the image section D.sub.2 of FIG. 1b shown in FIG. 2b, a third embodiment of the calibration piece 10 can be seen, which is arranged on the workpiece carrier 20. The third embodiment shown in FIG. 2b has a cuboid base body, the base body having a first groove 11 with a rectangular cross section. The base body of this third embodiment of the calibration piece further comprises a second groove 12, which extends perpendicularly to the first groove 11 and opens into the first groove 11, said second groove 12 having a trapezoidal cross-section. On a side of the calibration piece 10 opposite the side having the groove 11, the calibration piece 10 has a further groove 11 which runs parallel to the groove 11. Perpendicular to groove 11 runs a further groove 12 with a rectangular cross-section, which opens into groove 11. As can be seen from FIG. 1b, this third embodiment of the calibration piece 10 is arranged on the workpiece slide in such a way that the second groove 12 runs parallel to the workpiece spindle axis A, thus imitating the shape and orientation of a tooth gap in a workpiece to be machined. To determine the response behaviour of the meshing sensor 1, the meshing sensor 1 can be moved on a side of the calibration piece 10 having the grooves 11 and 12 in a tangential direction along the groove 11 and/or in a Z.sub.M direction (which corresponds to an axial direction with respect to the workpiece spindle 21) and/or in a Y.sub.M direction (which corresponds to a radial direction with respect to the workpiece spindle 21). As indicated in FIG. 1b, this embodiment of the calibration piece can also be attached to the workpiece carrier (20) rotated by 180, whereby the groove 12 with the rectangular cross-section is then oriented towards the meshing sensor 1 during the calibration method.
[0073] In the image section D.sub.3 of FIG. 1b shown in FIG. 2c, a fourth embodiment of the calibration piece 10 can be seen, which is detachably arranged in the clamping means 22. This fourth embodiment of the calibration piece 10 is disk-shaped and has an outer profile with calibration teeth 13,13. In this embodiment, two calibration teeth 13,13 are located radially opposite each other, the first calibration tooth 13 having a rectangular shape, while the second calibration tooth 13 has a trapezoidal shape. The calibration teeth 13,13 are aligned in the Y.sub.M direction. To determine the response behavior of the meshing sensor 1, it can be moved in a tangential direction with respect to the workpiece spindle (X.sub.M-direction), whereby the meshing sensor 1 aligned antiparallel to the Y.sub.M-direction can scan one of the two calibration teeth (here the one with the rectangular shape, 13) without contact. If scanning of the calibration tooth 13 (trapezoidal shape) is preferred, the calibration piece can be arranged rotated by 180.
[0074] In the image section D.sub.4 of FIG. 1b shown in FIG. 2d, a fifth embodiment of the calibration piece 10 can be seen, which is arranged on the clamping means 22. The fifth embodiment of the calibration piece 10 has a cuboid projection 14 which extends radially from a surface of the clamping means 21, the cuboid projection 14 being flanked by two orientation areas projecting into the surface of the clamping means. In the embodiment example shown here, the projection points in the Y.sub.M direction and the flanking orientation areas 15 are arranged on both sides of the projection 14 with respect to the tangential direction in such a way that the orientation areas 15 lie in the X.sub.M/Z.sub.M plane.
[0075] FIG. 2e shows a perspective view of a machine tool 2 with a sixth embodiment of the calibration piece, which is arranged on the workpiece spindle housing 211. As can be seen in the enlargement of the image section D.sub.5 in FIG. 2f, this sixth embodiment of the calibration piece has a cylindrical base body, which is arranged on a cuboid carrier 17. The cylindrical base body has a cylinder axis 16, which runs parallel to the Y.sub.M axis in this case.
[0076] FIG. 2g shows a side view of a machine tool 2 with a seventh embodiment of the calibration piece, which is arranged on the workpiece spindle housing 211. As can be seen in the enlargement of the image section D.sub.6 in FIG. 2h, this seventh embodiment of the calibration piece has a dome-shaped base body which is arranged on a cuboid carrier 17, the dome-shaped base body pointing in the Y.sub.M direction.
[0077] FIGS. 3a and 3b show a preferred arrangement of the calibration piece 10, which corresponds to the first embodiment in FIG. 2a, in the machine tool 2, with FIG. 3b showing an enlargement of the section F framed in FIG. 3a. The sensor positioning arm 251 has a sensor holder 26, which forms a mechanical receptacle for a sensor carrier 27. As can be seen in FIG. 3c, the sensor carrier 27 has a stop element 271 which serves as a positioning aid for mounting the sensor carrier 27 in the sensor holder 26. The meshing sensor 1 has a meshing sensor surface O and is mounted in the sensor carrier 27 in such a way that the meshing sensor surface O is at a defined distance e from the stop element 271. Such a sensor carrier 27 forms a uniform interface to the sensor holder 26 for meshing sensors 1 of different sizes. If the meshing sensor 1 has to be replaced, it can be removed from the sensor holder 26 together with the sensor carrier 27. A new meshing sensor is then installed in the sensor carrier 27 in such a way that its meshing sensor surface is also at the same defined distance e from the stop element 271, which can be checked by a suitable measuring means before the sensor carrier 27 is reinstalled in the sensor holder 26. As can be seen in FIGS. 3a and 3b, the sensor positioning device 25 with the meshing sensor 1 in the sensor holder 26 can be moved without collision to the calibration piece 10 despite a machining tool 28 arranged on the tool holder 24 in order to scan the calibration piece 10 along the directions X.sub.M, Y.sub.M and Z.sub.M without contact, with the meshing sensor 1 aligned antiparallel to the Y.sub.M direction.
[0078] FIGS. 4a-4d illustrate in a schematic (not to scale) manner a method for calibrating a contactless meshing sensor 1 that outputs switching signals in accordance with the present invention. The meshing sensor shown in this embodiment has a switching region B which extends from a meshing sensor surface O to a switching interface G shown here as a dashed line and defines a fictitious sensor axis A.sub.S. If material enters the switching region B, the switching signal output by the meshing sensor 1 changes. In order to be able to reliably determine the phase position of the teeth of a pre-toothed workpiece 23 with tip circle K, the workpiece measuring position P.sub.W is to be calculated in such a way that a response behavior of the meshing sensor 1 that is as symmetrical as possible is achieved. Such a symmetrical response behavior is achieved if the fictitious sensor axis A.sub.S coincides with a predefined measuring axis A.sub.M (here parallel to the Y.sub.M direction at a predefined height in the Z.sub.M direction), and if the meshing sensor surface O is spaced apart from the tip circle K by a predefined measuring distance d such that the tip circle K crosses the switching region B (see FIG. 4a).
[0079] According to the present invention, the fictitious sensor axis A.sub.S of the meshing sensor 1 is determined on the basis of the calibration piece 10, the calibration piece 10 having a known geometry and being located at a known calibration point C.sub.M in the coordinate system K.sub.M of the workpiece carrier. For this purpose, the meshing sensor 1 is brought into the vicinity of the calibration piece.
[0080] Possible steps of a calibration procedure are shown in FIGS. 4b-4d:
In this example, a peak switching point S of the switching region is first determined in a first step (FIG. 4b) by approaching an end face F of the calibration piece 10, the end face here lying in the X.sub.M-Z.sub.M plane. If a theoretical position of the meshing sensor 1 in the coordinate system K.sub.M of the workpiece carrier is already known, for example because it has been determined by a geometric measurement in the machine and stored in the sensor controller, the determination of the peak switching point S can also be omitted, since the known theoretical position of the meshing sensor 1 allows the latter to be moved directly to a predefined calibration position Pc. However, the meshing sensor can also be in an instantaneous position that deviates from the theoretical position; for example, if the machine is in a different temperature state than during the determination of the theoretical position. Likewise, the instantaneous position of the meshing sensor can deviate from the theoretical position if there is an installation error; for example, if the meshing sensor surface O does not have the intended distance e from the stop element shown in FIG. 3c, or if the stop element 271 of the sensor carrier 27 has not been mounted flush against the sensor holder 26. By determining the peak switching point S in the coordinate system K.sub.M of the workpiece carrier, such installation errors can be detected.
[0081] In a second step (FIG. 4c and FIG. 4d), the meshing sensor 1 is moved antiparallel to the Y.sub.M direction closer to the calibration piece 10, ideally in such a way that the meshing sensor surface O is spaced apart from the end face F by the predefined measuring distance d, which should then also occur between the meshing sensor surface O and a tip circle K of the workpiece 23 when the meshing sensor 1 (as shown in FIG. 4a) is in the workpiece measuring position P.sub.W.
[0082] In a third step, flank switching points are determined which are located on the switching interface G of the switching region B of the meshing sensor in the X.sub.M and Z.sub.M directions. In a simple embodiment of the calibration method, this third step is performed at a single measuring distance d in the Y.sub.M direction, whereby two flank switching points each are preferably determined in the X.sub.M direction and in the Z.sub.M direction. FIG. 4c shows as an example how the meshing sensor is moved past a first flank k.sub.1 of the calibration piece parallel to the X.sub.M direction to determine a first flank switching point S.sub.F1, while FIG. 4d shows how the meshing sensor is moved past a second flank k.sub.2 of the calibration piece anti-parallel to the X.sub.M direction to determine a second flank switching point S.sub.F2. By moving the meshing sensor 1 along the Z.sub.M direction, two further flank switching points can be determined in the same way. The determined flank switching points are stored in a memory 31 of the sensor controller 3. A theoretical central point S.sub.Z of the switching region B can then be determined from the stored flank switching points. A fictitious axis A.sub.S is placed through this theoretical central point S.sub.Z, whereby this fictitious axis A.sub.S is normal to the X.sub.M-/Z.sub.M-plane.
[0083] For the measurement on the workpiece, the meshing sensor is then brought into the workpiece measuring position P.sub.W in such a way that this fictitious sensor axis A.sub.S comes to lie on the desired measuring axis A.sub.M, and as shown in FIG. 4a ideally in such a way that the central point S.sub.Z comes to lie on a point of intersection of the measuring axis A.sub.M with the tip circle K, thus achieving a response behavior of the meshing sensor 1 that is as symmetrical as possible.
[0084] FIG. 5 shows the above-described example of a calibration method of a meshing sensor 1 in a machine tool 2 for machining pre-toothed workpieces, for the execution of which the machine tool is designed according to one embodiment of the present invention. First, a measuring axis A.sub.M and a measuring distance d are defined 101 in the coordinate system K.sub.M of the tool carrier, and the calibration point C.sub.M is determined 102 at which the calibration piece 10 is arranged. Subsequently, the meshing sensor 1 is moved toward an end face F of the calibration piece 200 and a peak switching point S of the switching region B is determined 201. Then the meshing sensor 1 is positioned in such a way that the meshing sensor surface O is spaced from the end face of the calibration piece 10 by the measuring distance d 202. Now the meshing sensor 1 is moved along the calibration piece 10 to scan it without contact 203. Meanwhile, the meshing sensor 1 outputs switching signals from which flank switching points are determined 204. A fictitious sensor axis A.sub.S is then determined from these flank switching points 205. In a final step 206, the meshing sensor 1 is brought into a workpiece measuring position P.sub.W calculated by the sensor controller 3, in which the determined fictitious sensor axis A.sub.S coincides with the measuring axis A.sub.M.
LIST OF REFERENCE SIGNS
[0085]
TABLE-US-00001 1 meshing sensor 271 stop element 2 machine tool 28 machining tool 3 sensor controller 30 scanning means 10 calibration piece 31 memory 11, 11 first groove K.sub.M coordinate system of the 12, 12 second groove workpiece carrier 13, 13 calibration tooth C.sub.M calibration point 14 projection P.sub.W workpiece measuring position 15 orientation area P.sub.C calibration position 16 cylinder axis A workpiece spindle axis 17 cuboid carrier A.sub.M measuring axis 20 workpiece carrier A.sub.S fictitious sensor axis 21 workpiece spindle B switching region 211 workpiece spindle housing d measuring distance 212 workpiece spindle shaft F end face 22 clamping means O meshing sensor surface 23 workpiece G switching interface 24 tool carrier S peak switching point 241 tool spindle S.sub.Z central point 25 sensor positioning device S.sub.F1, flank switching points S.sub.F2 251 sensor positioning arm k.sub.1, flanks k.sub.2 26 sensor holder 27 sensor carrier
