Machine tool for machining gears, method for machining tooth flanks of a workpiece, and method for dressing a tool for machining gears using such a machine

Description

TECHNICAL FIELD

[0001] The present invention relates to a machine tool according to the preamble of claim 1 for machining gears, methods for its operation, and a computer program for carrying out the methods. STATE OF THE ART

[0002] In gear technology, straight or helical gears are often manufactured with tooth flanks modified to create a crown. The size of these modifications is often only a few tens of micrometers. Such modified gears offer particular advantages in terms of load behavior and noise generation.

[0003] For the production of wide-crowned modified gears, a method was proposed in the prior art in which the center distance between the workpiece and the tool is continuously varied along a radial feed direction during a machining stroke. To this end, the prior art proposed performing a movement along the radial feed direction during the machining stroke, initially increasing the center distance, stopping in the center of the gear, and then reducing the center distance again while the tool is continuously advanced parallel to the workpiece axis.

[0004] This process is problematic in that the direction of the radial feed movement reverses during the machining stroke. A large number of components are involved in the radial feed movement, between which elastic forces and frictional forces occur. During the reversal of direction, a transition from sliding friction to static friction takes place, particularly at the seals involved. This means that after the reversal of direction, static friction must first be overcome before sliding friction sets in again. As a result, the radial feed movement cannot fully follow the target specifications at the reversal point and comes to a complete standstill for a certain period of time until the acting forces overcome the static friction force again. This effect can lead to undesirable deviations of the flank form from the specifications.

[0005] Particularly in finishing operations where only a very small stock is removed, the machining forces may be relatively small. This can lead to a load change when reversing the direction along the radial infeed direction, which leads to an additional undesirable reversal effect due to the finite stiffness of the components involved.

[0006] In addition, frictional effects can occur during very slow radial infeed movements, even independent of the direction reversal. These effects, combined with elastic forces, can lead to friction-induced vibrations. Such effects also occur in the production of modifications other than wide-crowned modifications, such as conical modifications.

[0007] These effects can be counteracted through various measures. In particular, particularly low-friction guide and drive components can be used to reduce friction effects. To reduce reversal effects, the stiffness of the guide and drive components can be increased or optimized together with the damping. Finally, these effects can also be counteracted through control technology. However, all of these measures only mitigate the aforementioned problems; they cannot completely eliminate them.

[0008] DE 10 2012 016515 A1 discloses a machine tool according to the preamble of claim 1, namely a gear shaping machine whose shaping head slide is mounted on a machine stand in an inclined position. In this way, a displacement in the vertical direction achieves a simultaneous displacement of the shaping tool in the horizontal direction in order to lift the shaping tool from the workpiece during the return stroke. The creation of modifications is not addressed.

[0009] US 2016 / 176010 A1 discloses a generating grinding machine with two workpiece spindles and one tool spindle. The tool spindle is mounted for displacement along a linear guide extending parallel to a horizontal inclined axis. The workpiece spindles are positioned at the same vertical horizontal distance from the horizontal inclined axis. In a horizontal projection, the tool rotation axis forms an acute angle to the horizontal inclined axis. This prevents collisions between the tool spindle and the workpieces. The generation of modifications is also not addressed here. DESCRIPTION OF THE INVENTION

[0010] It is an object of the present invention to provide a gear cutting machine which enables the production of modified tooth flanks with higher precision.

[0011] This object is achieved by a machine tool for machining gears according to claim 1. Further embodiments are specified in the dependent claims.

[0012] A machine tool for machining gears is proposed. It features: a workpiece spindle for driving a workpiece to rotate about a workpiece axis; a tool spindle for driving a tool (machining tool) to rotate about a tool axis; and an axial slide with which a relative axial feed position between the tool spindle and the workpiece spindle with respect to the workpiece axis can be changed.

[0013] According to the invention, the axial slide is guided along an axial guide direction that is inclined relative to the workpiece axis at an angle of inclination. The angle of inclination has a value between 0.1° and 30°, preferably between 0.1° and 15°, and particularly preferably between 0.1° and 3°. In some embodiments, the angle of inclination has a value between 0.5° and 30°, between 0.5° and 15°, or between 0.5° and 3°.

[0014] The axial slide supports either the workpiece spindle or the tool spindle. Due to the inclined guide of the axial slide, the radial distance between the tool axis and the workpiece axis changes as the axial slide moves along the axial guide direction. This makes it possible to machine gears with tooth trace modifications without having to reverse the direction of the radial feed movement during gear machining. The problems mentioned above that arise when reversing the direction are thus avoided. Furthermore, it becomes possible to manufacture even the smallest tooth trace modifications without disruptive friction effects.

[0015] The machine tool also features an infeed slide, which allows the center distance between the tool axis and the workpiece axis to be further varied along an infeed direction. This infeed can occur independently of the movement along the axial guide direction. It is superimposed on the change in the center distance due to the inclined guide of the axial slide. Accordingly, during the machining of the tooth flanks, the axial slide and the infeed slide move simultaneously.

[0016] The feed direction can, but does not have to, be perpendicular to the workpiece axis. It is referred to below as the "radial feed direction," even though this direction is not necessarily exactly radial to the workpiece axis, i.e., not necessarily exactly perpendicular to the workpiece axis. For example, the radial feed direction can form an angle with the workpiece axis in the range of 60° to 120°.

[0017] The axial guide direction preferably runs in a common plane with the workpiece axis and the radial feed direction. The inclination angle can be positive or negative in this plane, i.e., the axial guide direction can be inclined away from or toward the workpiece axis (as viewed from the machine bed).

[0018] Preferably, the tool spindle is mounted directly or indirectly (i.e., via additional slides and / or swivel bodies) on the axial slide, meaning the tool spindle executes movements along the inclined axial guide direction relative to a machine bed of the machine tool. In this case, the axial slide forms a tool carrier. However, it is also conceivable for the workpiece spindle to be mounted directly or indirectly on the axial slide, meaning that the workpiece spindle executes movements along the inclined axial guide direction relative to the machine bed.

[0019] In particular, the following axis arrangement can be present: The feed slide can be guided on the machine bed so as to be displaceable along the radial feed direction and form a tool carrier, and the axial slide can then be arranged on the feed slide so as to be guided along the axial guide direction.

[0020] In advantageous embodiments, the tool spindle can be pivoted about a pivot axis relative to the axial slide. For this purpose, the machine tool can have a pivot body. The pivot body can in particular be arranged on the axial slide. If the tool is a grinding tool, the pivot body is also referred to as a grinding head. The pivot axis preferably runs parallel to the radial feed direction or perpendicular to the workpiece axis. However, it can also run at an angle to the radial feed direction that deviates from 0°, with this angle preferably being between 0° and 30°. The pivot axis can also run at an angle to the workpiece axis that deviates from 90°, with this angle preferably being in the range of 60° to 120°. In particular, the pivot axis can run perpendicular to the axial guide direction.It is advantageous if the swivel axis lies in a plane that is spanned by the workpiece axis and the axial guide direction.

[0021] In one embodiment, particularly suitable for continuous generating grinding, the tool spindle is displaceable relative to the axial slide along a shift direction that runs parallel to the tool axis. For this purpose, the machine tool may have a shift slide. The shift slide may, in particular, be mounted on the pivoting body such that it is displaceable relative to the pivoting body along the shift direction. The shift direction preferably runs perpendicular to the pivot axis about which the tool spindle is pivotable. In some embodiments, it also runs perpendicular to the radial feed direction.

[0022] The present invention also provides a method for machining tooth flanks of a workpiece using a machine tool of the type specified above. The method comprises: Executing a machining stroke by performing a movement between the tool spindle and the workpiece spindle along the inclined axial guide direction while a tool clamped on the tool spindle is in machining engagement with the workpiece clamped on the workpiece spindle; and performing an infeed movement between the tool spindle and the workpiece spindle along a radial infeed direction simultaneously with the machining stroke, wherein the movement along the inclined axial guide direction occurs at an axial guide speed and the movement along the radial infeed direction occurs at a radial infeed speed.

[0023] The machine has a control device which is designed to control the machine tool in such a way that it carries out corresponding simultaneous movements between the tool spindle and the workpiece spindle along the inclined axial guide direction and the radial feed direction.

[0024] Preferably, the sign of the axial guide speed does not change during a machining stroke. The sign of the radial infeed speed also preferably does not change during a machining stroke. According to the invention, the radial infeed speed during a machining stroke (and thus during the machining of each individual tooth flank) does not fall below a predetermined threshold value. This avoids adverse effects during the radial infeed movement. As a result, tooth trace modifications can be manufactured with much greater precision than with the prior art.

[0025] Particular advantages arise when the radial infeed speed and the axial guide speed are in a temporally variable relationship. In particular, these speeds can be in a variable relationship such that the radial infeed speed does not change its sign during a machining stroke (and thus during the machining of a tooth flank), while a resulting movement between the tool spindle and the workpiece spindle along the radial infeed direction has a speed that changes its sign during the machining of the tooth flanks (or during a machining stroke). This allows, in particular, wide-crowned modified gears to be manufactured without the above-described disadvantages of the prior art.

[0026] The procedure may include: Measuring position variables along the radial feed direction and the inclined axial guide direction; and transforming the measured position variables into transformed position variables along the radial feed direction and an axial feed direction parallel to the workpiece axis.

[0027] The procedure may also include: Generating control commands for a movement of the tool spindle relative to the workpiece spindle along an axial feed direction parallel to the workpiece axis; and transforming the generated control commands into transformed control commands for a simultaneous movement of the tool spindle along the inclined axial guide direction and the radial feed direction.

[0028] These measures make it possible to control the machine with a control device designed for machines whose axial guide direction runs parallel to the workpiece axis direction.

[0029] The control device of the machine tool may accordingly comprise at least one of the following transformation devices: a first transformation device for transforming position variables measured along the radial feed direction and the inclined axial guide direction into transformed position variables along the radial feed direction and an axial feed direction parallel to the workpiece axis; and a second transformation device for transforming control commands for a movement of the tool spindle relative to the workpiece spindle along an axial feed direction parallel to the workpiece axis into transformed control commands for a simultaneous movement of the tool spindle along the inclined axial guide direction and the radial feed direction.

[0030] The machine tool can be designed, in particular, for one of the following processes: continuous generating grinding, partial generating grinding, discontinuous or continuous profile grinding, gear honing, hobbing, or gear skiving. For this purpose, a corresponding tool can be mounted on the tool spindle. The control device can be designed to control the machine tool in such a way that it executes the movements of the tool spindle and the workpiece spindle typical for the respective process.

[0031] The machine tool can have a dressing device with a dressing tool. The control device can then be configured to dress the tool, in particular a grinding worm, with the dressing tool, generating movements along the inclined axial guide direction. During dressing, relative movements are thus generated between the tool and the dressing tool along the inclined axial guide direction while the tool is in engagement with the dressing tool. This allows similar advantages to those achieved during gear machining to be achieved during dressing.

[0032] In particular, the control device can be designed to align the tool spindle with its pivot axis relative to the axial slide in such a way that the tool axis runs in or parallel to a plane spanned by the axial guide direction and the radial feed direction. This position of the tool spindle is referred to below as the dressing position. The specified choice of dressing position is particularly advantageous when the tool is a grinding worm. During the dressing process, the grinding worm can thus be easily moved along its longitudinal axis, i.e. along the tool axis, along the inclined axial guide direction relative to the dressing tool in order to be able to dress the grinding worm across its entire width. The axial slide can be used for this purpose.If the tool spindle is mounted on a shift slide, the shift slide can be used alternatively or additionally, depending on the design.

[0033] The dressing device can have a dressing spindle designed to drive the dressing tool to rotate about a dressing spindle axis. The dressing spindle is preferably pivotable about at least one pivot axis in order to bring the dressing tool into engagement with the machining tool when the tool spindle is in the dressing position specified above. For this purpose, the dressing device can have a corresponding pivot body. The pivot axis of the dressing spindle preferably runs transversely to the axial feed direction, in particular at an angle of 60° to 120° to the axial feed direction, and transversely to the workpiece axis, preferably at an angle of 60° to 120° to the workpiece axis, in particular perpendicular to the latter. If the workpiece axis runs vertically in space, the pivot axis of the dressing spindle preferably runs horizontally.

[0034] The dressing device can be mounted together with the at least one workpiece spindle on a movable tool carrier, or it can be arranged stationary relative to the machine bed.

[0035] The present invention further provides a computer program. The computer program comprises instructions that cause a control device in a machine tool of the type described above, in particular one or more processors of the control device, to execute the method described above. The computer program can be stored in a suitable storage device.

[0036] Furthermore, the invention provides a computer-readable medium on which the computer program is stored. The medium may be a non-volatile medium, for example, a flash memory, a CD, a hard disk, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Preferred embodiments of the invention are described below with reference to the drawings, which are for illustrative purposes only and are not to be construed as limiting. In the drawings: Fig. 1 is a schematic perspective view of a generating grinding machine according to a first embodiment; Fig. 2 is a schematic side view of the generating grinding machine from Fig. 1 ; Fig. 3 a diagram illustrating a coordinate transformation during the machining of a cylindrical spur gear; Fig. 4 a schematic side view of a spur gear with wide crowned modified toothing; Fig. 5 a diagram illustrating a coordinate transformation during the machining of a spur gear according to Fig. 4; Fig. 6 is a schematic block diagram of functional units for controlling the axial feed movement; Fig. 7 is a schematic side view of a generating grinding machine according to a second embodiment; Fig. 8 is a schematic side view of a generating grinding machine according to a third embodiment; and Fig. 9 is a schematic side view of a generating grinding machine according to a fourth embodiment. DESCRIPTION OF PREFERRED EMBODIMENTS Example structure of a generating grinding machine

[0038] In the Figures 1 and 2As an example of a machine tool for machining gears, a generating grinding machine 1 according to a first embodiment is shown. The machine has a machine bed 4, on which a tool carrier 5 is guided so as to be displaceable along a radial feed direction X by means of linear guides 6. The tool carrier 5 carries an axial slide 7, which is guided so as to be displaceable relative to the tool carrier 5 along an axial guide direction Z'. A grinding head 9 is mounted on the axial slide 7, which grinding head can be pivoted about a pivot axis A running parallel to the X direction in order to adapt to the helix angle of the gear to be machined. The grinding head 9, in turn, carries a shift slide, on which a tool spindle 11 can be shifted along a shift direction Y. The shift direction Y runs perpendicular to the pivot axis A and thus also perpendicular to the X direction, but not necessarily perpendicular to the Z' direction.A finishing tool in the form of a helically profiled grinding wheel (grinding worm) 12 is clamped on the tool spindle 11. The grinding worm 12 is driven by the tool spindle 11 to rotate about a tool axis B. The tool axis B runs parallel to the Y-direction.

[0039] The machine bed 4 furthermore carries a pivotable workpiece carrier 15 in the form of a turret, which can be pivoted about a vertical axis C3 between at least two positions. Two identical workpiece spindles 16, 17 are mounted diametrically opposite each other on the workpiece carrier 15. The Fig. 2The workpiece spindle 16 arranged on the left is in a machining position in which a workpiece 18 clamped thereon can be machined with the grinding worm 12. To this end, this workpiece spindle drives the workpiece 18 to rotate about a vertical first workpiece axis C1. The other workpiece spindle 17, arranged offset by 180°, is in a workpiece change position in which a finished workpiece 19 can be removed from this spindle and a new blank can be clamped. The axis of the workpiece spindle in this position is referred to as the second workpiece axis C2.

[0040] Also mounted on the turret is a dressing device 13, indicated only symbolically, with a dressing tool 14. This serves to dress the grinding worm 12.

[0041] All driven linear and rotary axes of the generating grinding machine 1 are digitally controlled by a machine control system with control panel 2 and axis modules 3. The axis modules 3 provide control signals for one machine axis each (i.e., for at least one actuator used to drive the respective machine axis, such as a servo motor) at their outputs. Machining a workpiece

[0042] In order to machine an as yet unmachined, pre-toothed workpiece (blank) 19, the workpiece 19 is clamped by an automatic workpiece changer onto the workpiece spindle 17 located in the workpiece change position. The workpiece change takes place in parallel with the machining of another workpiece 18 on the other workpiece spindle 16, which is in the machining position. Once the newly machined workpiece 19 is clamped and machining of the other workpiece 18 is complete, the workpiece carrier 15 is pivoted 180° about the C3 axis so that the spindle with the newly machined workpiece moves into the machining position. Before and / or during the pivoting process, a centering operation is carried out using a centering probe (not shown in the drawing) arranged on the workpiece carrier 15.For this purpose, the workpiece spindle 17 is rotated, and the position of the tooth gaps of the workpiece 19 is measured using the centering probe. The pitch angle is determined on this basis.

[0043] When the workpiece spindle 17, which carries the workpiece 19 to be machined, has reached the machining position, the workpiece 19 is brought into engagement with the grinding worm 12 by moving the tool carrier 5 along the X-axis. The workpiece 19 is then machined by the rotating grinding worm 12 in rolling engagement. The machine executes coordinated movements along the X, Y, and Z axes. Machining can be performed in one or more axial machining strokes. During each machining stroke, the machine executes a movement along the Z' axis, the speed of which does not change its sign.

[0044] At the same time as the workpiece is being machined, the finished workpiece 18 is removed from the other workpiece spindle 16, and another blank is clamped onto this spindle. Axis directions

[0045] In addition to the X, Y, and Z' directions already mentioned, a further direction, Z, is defined. By definition, this runs parallel to the workpiece axis C1, i.e., the rotational axis of the workpiece in the machining position. Due to the machining stroke along the Z' axis, the position of the tool relative to the workpiece is continuously changed along the Z direction during machining of the workpiece in order to machine the gear teeth across the entire width of the workpiece. This is referred to as the axial feed, and the Z direction is therefore also referred to as the axial feed direction.

[0046] In the prior art, the axial guide direction Z', i.e. the direction along which the axial slide 7 is displaceably guided, usually coincides with the axial feed direction Z. In the present machine, however, these directions differ from one another. Specifically, the Z' direction runs within a plane spanned by the X direction and the Z direction and is inclined by an angle ψ with respect to the Z direction. The amount of ψ lies between 0.1° and 30°, in particular between 0.1° and 30°, preferably between 0.1° and 15°. A relatively small angle can suffice, e.g. between 0.1° and 3°, in particular between 0.5° and 3°.

[0047] For the arrangement of the directions X, Y, Z, Z', A, B and C1 proposed here, the following applies overall: X ⊥ Y, X ⊥ Z, Y ∦ ZA ∥ X, B ∥ Y, C1 ∥ ZA ⊥ B, A ⊥ C1, B ∦ C1 Z' ∦ Z, Z' ≮ X, Z' lies in the XZ or X-C1 plane

[0048] The symbol ∥ means "is parallel to", the symbol ∦ means "is not parallel to", the symbol ⊥ means "is perpendicular to" and the symbol ≮ means "is at an angle not equal to 0° and not equal to 90°". Coordinate transformation

[0049] The machine control normally calculates the corresponding control commands in the X, Y, Z coordinate system for a desired flank shape of the gear. In the present machine, a pure feed movement along the Z-direction requires simultaneous Movements along the X and Z directions. In order to operate this machine without having to rewrite all machine programs, the machine control is advantageously designed to transform the usual feed commands for movements along the Z direction into transformed control commands for simultaneous movements along the X and Z directions.

[0050] This will be explained below using the Figure 3It is assumed that the tool moves at a constant speed v Z along the Z-direction and with constant axial distance to the workpiece from an initial position with coordinates x = x 0 , z = z 0 to a final position with coordinates x = x 0 , z = z 1. The corresponding movement profile 31 is shown in part (a) of the Fig. 3 illustrated. Such a motion profile is selected when a cylindrical spur gear is to be machined without modifying its flanks by additional axis movements.

[0051] In order to generate such a motion profile in the present machine, the drives must be operated simultaneously along the X and Z directions. This is described in part (b) of the Fig. 3As can be seen from this diagram, the axial slide 7 moves continuously along the positive Z'-direction, while the tool carrier 5 moves continuously in the direction of the negative X-direction (ie in Fig. 2 to the right) to compensate for the inclination of the axial guide direction Z'. Overall, the axial slide 7 is moved along the Z' direction at a constant speed from a location z 0 ′ to a place z 1 ′ while moving along the X-direction at constant speed from location x 0 to a location x 1. The following applies to the initial and final positions: z 1 ′ − z 0 ′ = z 1 − z 0 / cos ψ x 1 − x 0 = − z 1 − z 0 ⋅ tan ψ

[0052] The same applies to the speeds v Z ′ along the Z' direction and v X along the X-direction: v Z ′ = v Z / cos ψ v X = − v Z ⋅ tan ψ

[0053] The corresponding motion profile 31' along the X and Z' directions is shown in part (b) of the Fig. 3 illustrated.

[0054] On this basis, it is easily possible to transform feed commands along the Z direction into transformed feed commands along the X and Z' directions.

[0055] If the tool simultaneously performs a shift movement along the Y-axis, this movement remains unaffected by the transformation into the X, Y, Z coordinate system. Also unaffected are, for example, a swivel movement around the A-axis, if it were performed during machining, or a change in the rolling coupling angle to generate additional rotary movements between the workpiece and the tool.

[0056] Assuming that the coordinate origins of the Z and Z' directions coincide, position coordinates x, y, z in the coordinate system X, Y, Z can be transformed into position coordinates x', y', z' in the coordinate system X, Y, Z' as follows: x ′ = x − z ⋅ tan ψ y ′ = y z ′ = z / cos ψ

[0057] The inverse transformation T -1< is used when measurements are taken with a measuring system arranged along the X and Z' directions, and the X and Z coordinates of the axial slide 7 are to be determined based on such measurements. This inverse transformation may be necessary to transfer the measured coordinates to the machine control in the required form. In this case, the coordinates x, y, z in the X, Y, Z coordinate system are calculated from the coordinates x', y', z' in the X, Y, Z' coordinate system as follows: x = x ′ + z ′ ⋅ sin ψ y = y ′ z = z ′ ⋅ cos ψ Generation of a wide-crowned modification

[0058] In the following, the Figures 4 and 5 the creation of a wide-crowned modification on a cylindrical spur gear is explained.

[0059] A wide crowned modified spur gear 32 is symbolically shown in the Fig. 4The teeth of the spur gear are thicker in the middle than at the ends along the width direction (during machining, this is the Z-direction), and the flank lines of the tooth flanks are curved accordingly. Sometimes, due to manufacturing reasons, the tip diameter is also larger in the middle of the spur gear than at the edges, giving the spur gear an additional barrel-shaped outer contour. Fig. 4 The barrel-shaped outer contour is drawn extremely exaggerated to simplify the explanation of the principle. In reality, such modifications usually only vary in size by a few micrometers and are invisible to the naked eye.

[0060] It is known from the prior art to produce a wide-crowned modified spur gear by superimposing a slow radial feed movement in the X direction during the feed movement along the Z direction. Such a movement profile 33 is shown in part (a) of the Fig. 5 illustrated. A uniform axial feed motion at a constant speed along the Z direction is superimposed with an infeed motion along the X direction. This initially has a positive speed (coordinate x increases), which progressively decreases until the infeed speed becomes zero at the center of the width of the gear and changes sign (i.e., coordinate x decreases again).

[0061] Very low radial feed rates are problematic due to unavoidable friction effects. Reversing the direction of the feed motion is also problematic because the elements involved in guiding along the X-direction exhibit an unavoidable reversal effect.

[0062] In this machine, a reversal of the feed direction is avoided when making modifications, and the feed speed never falls below a certain minimum speed during gear machining, provided the required amount of crowning is not too large. This is described in part (b) of the Fig. 5, in which the resulting motion profile 33' is illustrated. The tool carrier 5 moves continuously in the negative X direction to compensate for the inclination of the Z' direction. The movement for generating the modification is superimposed on this continuous basic movement. However, the speed of the superimposed movement is always smaller in magnitude than the speed of the basic movement, so that a reversal of direction never occurs during gear machining and a certain minimum speed is never undercut. Functional units for controlling the axial feed movement and radial feed movement

[0063] The Figure 6schematically illustrates various functional units that are used to generate the axial feed movement along the Z direction and the radial infeed movement along the X direction. Position sensors 41, 42 detect the positions x', z' of the axial slide 7 along the X and Z directions. A first transformation device 43 transforms these positions in the X, Y, Z' coordinate system into the positions x and z in the X, Y, Z coordinate system by applying the inverse transformation T -1< and transfers these actual values ​​to a control computer 44 of the machine control system. The control computer 44 generates control signals Ax, Az that correspond to setpoints for the positions of the axial slide 7 in the X, Y, Z coordinate system. A second transformation device 45 transforms these control signals into transformed control signals Ax', Az' in the X, Y, Z' coordinate system and transfers these transformed control signals to the axis modules 3 of the machine control system. Application in dressing

[0064] It is known from the prior art to create modifications on the grinding worm flanks during dressing by means of appropriate axial movements in order to transfer these modifications to the workpiece flanks during subsequent machining using the diagonal method. For this purpose, it is known to engage a spatially stationary dressing device with a rotating dressing wheel with the grinding worm and to generate the required movements with the machine axes X and Y.

[0065] This machine allows for a different dressing strategy. For this dressing strategy, the grinding worm is rotated around the A-axis until the shift axis Y and the tool axis B are perpendicular, i.e., run along the Z-direction. The dressing device is aligned accordingly.

[0066] In the Fig. 2This is indicated by the dressing device 13, shown only symbolically and shown in dashed lines. The dressing device is mounted on the workpiece carrier (rotating turret) 15. It can be brought into a position opposite the grinding worm 12 by pivoting the turret through 90°. The dressing device 13 comprises a dressing spindle with a dressing wheel 14 mounted thereon, which is driven to rotate. The dressing spindle is mounted on a pivoting body 21. This is pivotally connected to the workpiece carrier in such a way that the dressing wheel 14 can be aligned in the direction of the worm threads and relative to the grinding worm profile. The corresponding pivot axis runs perpendicular to the workpiece axes C1, C2 and horizontally in space. Fig. 2the corresponding swivel axis runs perpendicular to the drawing plane. In addition, the dressing spindle can be swiveled about another swivel axis, which also runs horizontally in space and is perpendicular to the aforementioned swivel axis. Fig. 2 This additional swivel axis runs horizontally in the drawing plane. This additional swivel axis can be used, for example, to change the profile angle during dressing.

[0067] The required dressing movements along tool axis B are now generated not with the shift slide along the Y-axis as usual, but with the axial slide 7. Similar considerations apply to those outlined above for workpiece machining. In particular, this prevents a reversal of direction along the X-direction when making modifications to the grinding worm flank.

[0068] The present invention is also advantageous when dressing is carried out with a gear-shaped dressing wheel clamped on the workpiece spindle. Further applications

[0069] The advantages of the present invention were explained above using the example of the production of wide-crowned modified spur gears. However, the invention is not limited to this application, but can also be advantageously used in the production of other gears or gearwheels. In particular, the invention also has advantages in the production of gears modified in other ways, e.g., conically modified gears, since disruptive friction effects can be avoided with the invention in these cases as well. Second embodiment

[0070] In the Fig. 7A second embodiment of a generating grinding machine is shown schematically. This differs from the first embodiment in that the A-axis is not perpendicular to the Z-direction and parallel to the X-direction, but perpendicular to the Z'-direction and accordingly at an angle Ψ to the X-direction. As a result, the Y-axis and the tool axis B are no longer perpendicular to the X-direction as soon as the swivel angle around the A-axis differs from the Fig. 7 deviates from the position shown. Nevertheless, the advantages mentioned above can also be achieved with this arrangement. This embodiment is particularly suitable for small inclination angles between 0.1° and 3°.

[0071] Overall, in this embodiment, the arrangement of the directions X, Y, Z, Z', A, B and C1 is as follows: X ≮ Y, X ⊥ Z, Y ∦ ZA ≮ X, B ∥ Y, B ∦ C1, C1 ∥ ZA ⊥ B, A ⊥ Y, A ⊥ Z', A ≮ C1, A ≮ Z, A lies in X-C1 plane Z' ∦ Z, Z' ≮ X, Z' lies in X-C1 plane

[0072] Due to the inclined A-axis, additional coordinate transformations are necessary compared to the first embodiment to move from a coordinate system defined by the machine axes X, Y, Z', A, B, C1 to an orthogonal coordinate system or to a conventional coordinate system of the machine control system, and vice versa. However, the corresponding transformations can be easily derived using simple trigonometric considerations. Third embodiment

[0073] In the Fig. 8A third embodiment of a generating grinding machine is shown schematically. In this embodiment, the entire tool carrier 5, including the axial slide 7, shift slide, and grinding head 9, is of conventional construction. In particular, the axial guide direction Z' runs perpendicular to the feed direction X. Instead, the workpiece carrier (rotating turret) 15 is inclined relative to the vertical. As a result, in particular, the workpiece axis C1 and thus also the axial feed direction Z, which by definition runs parallel to the workpiece axis C1, no longer runs perpendicular to the X direction.

[0074] Compared to the first embodiment, this embodiment also requires additional coordinate transformations to convert from a coordinate system defined by the machine axes X, Y, Z', A, B, C1 to an orthogonal coordinate system or to a conventional coordinate system of the machine control system, and vice versa. The corresponding transformations can again be easily derived using simple trigonometric considerations. Fourth embodiment

[0075] In the Fig. 9A generating grinding machine according to a fourth embodiment is shown schematically. As in the first and second embodiments, the turret with the axes C1 and C3 is positioned vertically in space, and the axial slide 7 is guided relative to the tool carrier 5 along an axial guide direction Z', which runs at an inclination angle ψ to the vertical relative to the workpiece axis C1 running vertically in space. Unlike in the first and second embodiments, however, the entire tool carrier 5, including the axial slide 7, shift slide, and grinding head 9, is not guided exactly horizontally on the machine bed 4, but along a direction that runs at an inclination angle ψ to the horizontal. As in the embodiments discussed above, this guide direction is again referred to as the X direction. The X direction is therefore not perpendicular to the Z direction here, but perpendicular to the Z' direction.As in the first embodiment, the A-axis runs horizontally in space and thus perpendicular to the Z-direction. However, due to the inclined X-guide, the A-axis does not run parallel to the X-direction.

[0076] Overall, in this embodiment, the arrangement of the directions X, Y, Z, Z', A, B and C1 is as follows: X ≮ Y, X ≮ Z, Y ∦ ZA ≮ X, B ∥ Y, B ∥ C1, C1 ∥ ZA ⊥ B, A ⊥ Y, A 1Z, A ⊥ C1, A ≮ Z', A lies in X-C1 plane Z' ∦ Z, Z' ⊥ X, Z' lies in X-C1 plane

[0077] Compared to the first embodiment, this embodiment also requires additional coordinate transformations to convert from a coordinate system defined by the machine axes X, Y, Z', A, B, C1 to an orthogonal coordinate system or to a conventional coordinate system of the machine control system, and vice versa. The corresponding transformations can again be easily derived using simple trigonometric considerations. Variations

[0078] In the examples shown above, the inclination angle ψ is positive, i.e. the Z' axis is inclined towards the positive X direction or away from the workpiece axis C1.

[0079] This angle can also be negative. The transformations mentioned above remain valid in this situation. A negative inclination angle ψ can be particularly advantageous if the final finishing stroke is along the negative Z-direction (i.e. in the Figure 2 from top to bottom), since the tool carrier 5 is then moved along the negative X direction, i.e., toward the workpiece, to generate the compensation movement. This is advantageous because the radial machining forces counteract the compensation movement, resulting in defined force ratios in the components involved in generating the X movement.

[0080] The present invention is not limited to a specific machining method. The advantages of the invention were explained above with reference to continuous generating grinding. However, the invention also demonstrates its advantages in other processes for producing gears, including processes with a geometrically undefined cutting edge and processes with a geometrically defined cutting edge. Examples include pitch generating grinding, discontinuous or continuous profile grinding, gear honing, gear hobbing, or gear skiving. The invention can be used to manufacture both externally and internally toothed workpieces. The invention is particularly advantageously used in the fine machining of pre-toothed workpieces, in particular in hard fine machining.

[0081] The present invention is not limited to a specific axis sequence. Depending on the type of machine, it may also be advantageous, for example, to arrange the axial slide directly on the machine bed and to mount the workpiece spindle on a radial slide in order to achieve radial infeed through movement of the workpiece spindle.

[0082] The present invention is also not limited to the radial feed direction X running perpendicular to the workpiece axis C1. Thus, in the third and fourth embodiments, the radial feed direction X runs at an angle other than 90° to the workpiece axis C1. However, even in this situation, it is advantageous if the axial guide direction Z' runs in a common plane with the radial feed direction X and the workpiece axis C1.

[0083] Instead of two workpiece spindles, three or more workpiece spindles or just a single workpiece spindle can be present. The at least one workpiece spindle does not need to be arranged on a movable workpiece carrier, but can be arranged directly on the machine bed. In other embodiments, the at least one workpiece spindle is arranged on a movable workpiece carrier, which implements the radial feed movement along the X-direction. The A-axis can also be implemented on the workpiece side instead of the tool side.

[0084] The dressing device 13 can also be mounted on the machine bed instead of on a movable workpiece carrier. In this case, the tool carrier 5 can be pivoted relative to the machine bed to move the machining tool to the dressing tool, as is known per se, for example, from US5857894B.

[0085] From the above, it can be seen that a very large number of relative arrangements of the axes involved are possible. The invention is not limited to any specific arrangement.

[0086] Furthermore, the present invention is not limited to specific drive types for the various linear guides. The drive can be implemented in any manner known in the art, e.g., by ball screws or linear motors.

Claims

1. A machine tool (1) for machining gearing, comprising: a workpiece spindle (16) for driving a workpiece (18) for rotation about a workpiece axis (C1); a tool spindle (11) for driving a tool (12) for rotation about a tool axis (B), and an axial slide (7) configured to vary a relative axial feed position between the tool spindle (11) and the workpiece spindle (16) with respect to the workpiece axis (C1), wherein the axial slide (7) is guided along an axial guide direction (Z') which is inclined with respect to the workpiece axis (C1) by an angle of inclination (Ψ), the angle of inclination (Ψ) having an absolute a value of between 0.1° and 30° , in particular between 0.5° and 30° ; and an infeed slide (5), configured to vary a radial distance between the tool axis (B) and the workpiece axis (C1) along a radial infeed direction (X), wherein the axial guide direction (Z') preferably runs in a common plane with the workpiece axis (C1) and the radial infeed direction (X), and wherein the radial infeed direction (X) preferably runs at an angle of 60° to 120° to the workpiece axis (C1), in particular perpendicular to the workpiece axis (C1), characterized in that the machine tool comprises a control device (2, 3) which is configured to carry out the following method: causing simultaneous movements between the tool spindle (11) and the workpiece spindle (16) along the inclined axial guide direction (Z') and the radial infeed direction (X) while a tool (12) clamped on the tool spindle (11) is in machining engagement with the workpiece (18) clamped on the workpiece spindle, wherein the movement along the inclined axial guide direction (Z') is carried out at an axial guide speed and the movement along the radial infeed direction (X) takes place at a radial infeed speed, wherein the absolute value of the radial infeed speed during a machining stroke does not fall below a predetermined threshold value.

2. The machine tool (1) according to claim 1: a machine bed (4); wherein the infeed slide (5) is guided on the machine bed (4) so as to be displaceable along the radial infeed direction (X), forming a tool carrier; wherein the axial slide (7) is guided on the infeed slide (5) along the axial guide direction (Z').

3. The machine tool (1) according to claim 1 or 2, wherein the tool spindle (11) is pivotable about a swivel axis (A) relative to the axial slide (7), and wherein the swivel axis (A) extends in a common plane with the workpiece axis (C1) and the radial infeed direction (X), with an angle to the radial infeed direction (X) that has an absolute value between 0° and 30° in terms of magnitude, in particular parallel to the radial infeed direction (X), wherein the tool spindle (11) is preferably displaceable relative to the axial slide (7) along a shift direction (Y) running parallel to the tool axis (B), wherein the shift direction (Y) runs perpendicular to the swivel axis (A).

4. The machine tool (1) according to any one of the preceding claims, wherein the control device (2, 3) is configured to control the radial infeed speed and the axial guide speed in such a way that the radial infeed speed and the axial guide speed have a ratio that changes during the machining stroke.

5. The machine tool (1) according to any one of the preceding claims, wherein the control device (2, 3) is configured to control the radial infeed speed and the axial guide speed in such a way that the radial infeed speed does not change its sign during the machining stroke, while a resulting movement between the tool spindle (11) and the workpiece spindle (16) along the radial infeed direction (X) comprises a speed (vX) which changes its sign during the machining stroke.

6. The machine tool (1) according to any one of the preceding claims, wherein the control device (2, 3) comprises at least one of the following transformation devices: a first transformation device (43) for transforming position variables (x', z') measured along the radial infeed direction (X) and the inclined axial feed direction (Z') into transformed position variables (x, z) along the radial infeed direction (X) and an axial feed direction (Z) parallel to the workpiece axis (C1); and a second transformation device (45) for transforming control commands for a movement of the tool spindle (11) relative to the workpiece spindle (16) along an axial feed direction (Z) running parallel to the workpiece axis (C1) into transformed control commands (Ax', Az') for a simultaneous movement of the tool spindle (11) along the inclined axial feed direction (Z') and the radial infeed direction (X).

7. The machine tool (1) according to any one of the preceding claims, comprising a dressing device (13) with a dressing tool (14) wherein the control device (2, 3) is configured to dress the tool (12) with the dressing tool (14) while generating movements along the inclined axial guide direction (Z'), wherein the control device (2, 3) is preferably configured to bring the tool spindle (11) into a dressing orientation in which the tool axis (B) extends in or parallel to a plane spanned by the axial guide direction (Z') and the radial infeed direction (X).

8. The machine tool (1) according to claim 7, wherein the dressing device (13) comprises a dressing spindle which is configured to drive the dressing tool (14) for rotation about a dressing spindle axis, and wherein the dressing spindle is pivotable about at least one dressing swivel axis in order to bring the dressing tool (14) into engagement with the tool (12) when the tool spindle (11) is in the dressing orientation, wherein the dressing swivel axis preferably extends transversely to the axial feed direction (Z'), in particular at an angle of 60° to 120° to the axial feed direction.

9. The machine tool (1) according to any one of the preceding claims, wherein the machine tool is configured to carry out one of the following processes: continuous generation grinding, discontinuous generation grinding, discontinuous or continuous profile grinding, gear honing, hobbing or hob peeling.

10. A method for machining tooth flanks of a workpiece (18) with a machine tool (1) according to any one of the preceding claims, comprising: carrying out simultaneous movements between the tool spindle (11) and the workpiece spindle (16) along the inclined axial guide direction (Z') and the radial infeed direction (X) while a tool (12) clamped on the tool spindle (11) is in machining engagement with the workpiece (18) clamped on the workpiece spindle, wherein the movement along the inclined axial guide direction (Z') takes place at an axial guide speed and the movement along the radial infeed direction (X) takes place at a radial infeed speed, wherein the absolute value of the radial infeed speed during a machining stroke does not fall below a predetermined threshold value.

11. The method according to claim 10, wherein the radial infeed speed and the axial guide speed have a ratio which changes during the machining stroke, wherein the radial infeed speed and the axial guidance speed preferably have a time-variable ratio such that the radial infeed speed does not change its sign during the machining stroke, while a resulting movement between the tool spindle (11) and the workpiece spindle (16) along the radial infeed direction (X) has a speed (vX) which changes its sign during the machining stroke.

12. A method for dressing a tool (12) for machining gearing with a machine according to any one of claims 1 to 9, comprising: generating relative movements between the tool (12) and a dressing device (13) with a dressing tool (14) along the inclined axial guide direction (Z') while the tool (12) is engaged with the dressing tool (14) in order to dress the tool (12), wherein the tool spindle (11) is preferably brought into a dressing orientation before dressing, in which the tool axis (B) extends in or parallel to a plane spanned by the axial guide direction (Z') and the radial infeed direction (X).

13. The method according to any one of claims 10 to 12, wherein the method comprises: measuring position variables (x', z') along the radial infeed direction (X) and the inclined axial guide direction (Z'); and transforming the measured position variables (x', z') into transformed position variables (x, z) along the radial infeed direction (X) and an axial feed direction (Z) parallel to the workpiece axis (C1), and / or wherein the method comprises: generating control commands (Ax, Az) for a movement of the tool spindle (11) relative to the workpiece spindle (16) along an axial feed direction (Z) parallel to the workpiece axis (C1); and transforming the generated control commands into transformed control commands (Ax', Az') for simultaneous movement of the tool spindle (11) along the inclined axial guide direction (Z') and the radial infeed direction (X).

14. The method according to claim 10 or 11, said method being one of the following methods: continuous generation grinding, discontinuous generation grinding, discontinuous or continuous profile grinding, gear honing, hobbing or hob peeling.

15. A computer program comprising instructions which cause a control device (2, 3) of a machine tool (1) according to any one of claims 1 to 9 to execute a method according to any one of claims 10 to 14.