Machine tool for machining teeth, method for machining tooth surfaces of a workpiece, and method for dressing a tool for machining teeth using a machine tool of this type

Abstract

The present invention relates to a machine tool 1 for machining gears, comprising a work spindle 16 for driving a workpiece 18 in rotation about a work axis C1, and a tool spindle 11 for driving a tool 12 in rotation about a tool axis B. An axial carriage 7 is used to change the relative axial advance position between the tool spindle and the work spindle with respect to the work axis. The axial carriage is guided along an axial guiding direction Z' which is inclined to the work axis C1 by an inclination angle ψ, the inclination angle ψ being between 0.1° and 30°.

Description

[Technical Field]

[0001] The present invention relates to a machine tool for machining gears, to a method for operating the same, to a computer program for carrying out the method, and to a computer readable medium on which the computer program is stored. [Background technology]

[0002] In gear manufacturing technology, straight or helical gears are often produced whose tooth traces are modified by crowning. The degree of modification is often only in the range of less than a few tens of micrometers. Gears modified in this way have certain advantages with regard to load behavior and noise generation.

[0003] For the production of crowned gears, prior art processes have proposed that the center distance between the workpiece and the tool be continuously changed along the radial infeed direction during the machining stroke. Specifically, the prior art has proposed that during the machining stroke, the tool advances continuously parallel to the workpiece axis while making a movement along the radial infeed direction that first increases the center distance, reaches an intermediate stop in the gear train, and then decreases the center distance again.

[0004] This process is problematic in that the direction of the radial infeed movement reverses during the machining stroke. The radial infeed movement involves several components between which elastic and frictional forces occur. When the direction reverses, a transition from sliding friction to static friction occurs, particularly at the seals involved. As a result, once the direction changes, static friction must first be overcome before sliding friction can occur again. As a result, the radial infeed movement at the reversal point cannot fully comply with the desired specifications, but rather comes to a complete halt for a certain period of time until the application forces overcome the static friction forces again. This can lead to undesirable deviations in the profile shape from the specifications.

[0005] Particularly in finishing operations where only very small tolerances are removed, the machining forces can be relatively small, which can lead to load changes when the radial infeed direction is reversed, leading to further undesirable reversal effects due to the finite hardness of the components involved.

[0006] In addition, friction effects can occur even when there is no direction reversal, even at very slow radial infeed speeds, which, in combination with elastic forces, can lead to friction-induced vibrations.Such effects also occur when producing modifications other than crowning modifications, for example conical modifications.

[0007] These effects can be counteracted by various measures. In particular, special low-friction guide and drive components can be used to reduce the effects of friction. The stiffness of the guide and drive components can be increased or optimized together with damping to reduce the effects of reversal. Finally, these effects can also be counteracted by control algorithms. However, all these measures only lead to a reduction in the above-mentioned problems, but cannot completely eliminate them.

[0008] US Patent No. 5,949,999 discloses a gear forming machine in which the forming head carriage is mounted at an angle to the machine stand. In this way, vertical displacement causes a simultaneous displacement of the forming tool in the horizontal direction to lift the forming tool from the workpiece on the return stroke. The creation of corrections is not addressed.

[0009] Patent Document 2 discloses a generating gear grinding machine having two work spindles and one tool spindle. The tool spindle is slidably mounted along a linear guide extending parallel to the tilt axis in a horizontal plane. The work spindle is positioned at the same horizontal distance from the horizontal tilt axis. In horizontal projection, the tool rotation axis forms an acute angle with the horizontal tilt axis. This prevents collisions between the tool spindle and the workpiece. Again, the generation of modifications is not addressed. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] German Patent Publication No. 102012016515 [Patent Document 2] U.S. Patent Publication No. 2016 / 176010 Summary of the Invention

[0011] The object of the present invention is to provide a gear manufacturing machine which allows the production of modified tooth flanks with greater precision.

[0012] This object is achieved by a machine tool for machining gears according to claim 1. Further embodiments are specified in the dependent claims.

[0013] A machine tool for machining gears is proposed. a work spindle that rotates the work around the work axis; a tool spindle that rotates a tool (machining tool) around a tool axis; an axial carriage configured to change the relative axial feed position between the tool spindle and the work spindle with respect to the work axis; Equipped with.

[0014] According to the invention, the axial carriage is guided along an axial guiding direction inclined to the workpiece axis by an inclination angle. The inclination angle has a value between 0.1° and 30°, preferably between 0.1° and 15°, particularly preferably between 0.1° and 3°. In some embodiments, the inclination angle has a value between 0.5° and 30°, between 0.5° and 15°, or between 0.5° and 3°.

[0015] The axial carriage carries the work spindle or tool spindle. Due to the inclined guide of the axial carriage, the radial distance between the tool axis and the work axis changes when the axial carriage moves along the axial guide direction. This makes it possible to produce gears with modified tooth traces without having to reverse the direction of the radial infeed movement when machining the gear. This avoids the problems mentioned above that arise when the direction is reversed. Furthermore, it is possible to produce even the smallest tooth trace modifications without causing any significant friction effects.

[0016] Preferably, the machine tool comprises a feed carriage, the center distance between the tool axis and the workpiece axis of which can be further changed along the infeed direction. This infeed movement can be performed independently of the movement along the axial guide direction. The infeed movement is superimposed on the change in center distance due to the inclined guide of the axial carriage. Accordingly, simultaneous movements of the axial carriage and the feed carriage are performed when machining the tooth flank.

[0017] The infeed direction can be, but need not be, perpendicular to the workpiece axis. Hereinafter, the infeed direction will be referred to as the "radial infeed direction" even if this direction is not strictly radial to the workpiece axis, i.e., not strictly perpendicular to the workpiece axis. For example, the radial infeed direction can form an angle with the workpiece axis in the range of 60° to 120°.

[0018] The axial guiding direction preferably extends in a common plane with the workpiece axis and the radial feed direction, and the inclination angle in this plane may be positive or negative, i.e. the axial guiding direction may be inclined away from or towards the workpiece axis (as viewed from the machine bed).

[0019] Preferably, the tool spindle is arranged directly or indirectly (i.e. via a further carriage and / or a swivel) on the axial carriage, i.e. the tool spindle moves along an axial guide direction inclined relative to the machine bed of the machine tool. In this case, the axial carriage constitutes the tool carrier. However, it is also conceivable that the work spindle is mounted directly or indirectly on the axial carriage, i.e. the work spindle moves along an axial guide direction inclined relative to the machine bed.

[0020] In particular, the following axial sequence is possible: a feed carriage can be guided on the machine bed so that it is displaceable along the radial infeed direction and constitutes a tool carrier, and then an axial carriage can be arranged on the feed carriage so that it is guided along the axial guide direction.

[0021] In an advantageous embodiment, the tool spindle is configured to pivot about a pivot axis relative to the axial carriage. For this purpose, the machine tool can be provided with a pivoting body. In particular, the pivoting body can be arranged on the axial carriage. If the tool is a grinding tool, the pivoting body is also called a grinding head. The pivoting axis preferably extends parallel to the radial feed direction or perpendicular to the workpiece axis. However, the pivoting axis may also extend at an angle deviating from 0° relative to the radial feed direction. This angle preferably has an absolute value between 0° and 30°. The pivoting axis may also extend at an angle deviating from 90° relative to the workpiece axis. This angle is preferably in the range between 60° and 120°. In particular, the pivoting axis may extend perpendicular to the axial guide direction. Advantageously, the pivoting axis lies in the plane subtended by the workpiece axis and the axial guide direction.

[0022] In embodiments particularly suited for continuous generating grinding, the tool spindle can be moved relative to the axial carriage along a shift direction parallel to the tool axis. For this purpose, the machine tool can be equipped with a shift carriage. In particular, the shift carriage can be mounted on the swivel bed so that it can move relative to the swivel bed along the shift direction. The shift direction is preferably perpendicular to the pivot axis about which the tool spindle can be pivoted. In some embodiments, the shift direction is also perpendicular to the radial infeed direction.

[0023] The present invention also provides a method for machining a tooth flank of a workpiece using a machine tool of the type indicated above, the method comprising the steps of: performing a machining stroke by performing a movement between the tool spindle and the work spindle along an inclined axial guide direction while a tool clamped in the tool spindle is in machining engagement with a workpiece clamped in the work spindle; performing an infeed movement between the tool spindle and the work spindle along a radial infeed direction simultaneously with the machining stroke; Including, Movement along the inclined axial guide direction occurs at an axial guide speed, and movement along the radial infeed direction occurs at a radial infeed speed.

[0024] Therefore, the machine preferably comprises a control device designed to control the machine tool to effect corresponding simultaneous movements between the tool spindle and the work spindle along the inclined axial guide direction and the radial feed direction.

[0025] The sign of the axial guide speed preferably does not change during the machining stroke. The sign of the radial feed speed preferably also does not change during the machining stroke. It is advantageous if the radial feed speed during the machining stroke (and thus during the machining of each individual tooth flank) does not fall below a predetermined threshold value. This prevents negative effects during the radial feed movement. As a result, tooth trace modifications can be produced with increased accuracy compared to the prior art.

[0026] Certain advantages are obtained when the radial feed rate and the axial guide rate have a time-varying ratio. In particular, these rates can have a variable ratio such that the radial feed rate does not change its sign during the machining stroke (and thus during the machining of the tooth flank), but the resulting movement between the tool spindle and the work spindle along the radial feed direction has a rate that changes its sign during the machining of the tooth flank (or during the machining stroke). This makes it possible to produce gears, in particular with width crowning, without the above-mentioned disadvantages of the prior art.

[0027] The method comprises: measuring position variables along a radial feed direction and an inclined axial guide direction; - transforming the measured position variables into transformed position variables along a radial feed direction and an axial feed direction extending parallel to the workpiece axis; may include:

[0028] The method comprises: generating control commands for movement of the tool spindle relative to the work spindle along an axial feed direction parallel to the work axis; Transforming the generated control commands into transformed control commands for simultaneous movement of the tool spindle along an inclined axial guide direction and a radial feed direction; It can also include:

[0029] These measures make it possible to control the machine with a controller designed for machines whose axial guiding direction is parallel to the direction of the workpiece axis.

[0030] Therefore, the control device of the machine tool is a first conversion device for converting position variables measured along the radial feed direction and the inclined axial guide direction into converted position variables along the radial feed direction and the axial feed direction parallel to the workpiece axis; a second conversion device for converting control commands for movement of the tool spindle relative to the work spindle along an axial feed direction parallel to the work axis into converted control commands for simultaneous movement of the tool spindle along an inclined axial guide direction and a radial feed direction; The device is provided with at least one conversion device selected from the group consisting of:

[0031] In particular, the machine tool can be configured to perform one of the following processes: continuous generating grinding, part generating grinding, discontinuous or continuous form grinding, gear honing, hobbing, or hob peeling (gear skiving). For this purpose, a suitable tool can be clamped to the tool spindle. The control device can be configured to control the machine tool to perform tool spindle and work spindle movements typical for the respective process.

[0032] The machine tool may include a dressing device having a dressing tool. The control device may then be configured to use the dressing tool to dress a tool, in particular a grinding worm, and to cause movement along an inclined axial guide direction during dressing. Such dressing involves relative movement of the tool and the dressing tool along the inclined axial guide direction while the tool is engaged with the dressing tool. In this way, advantages similar to those in gear machining may be realized in dressing.

[0033] In particular, the control device can be configured to align the tool spindle with respect to the axial carriage using the associated pivot axis so that the tool axis is in or parallel to the plane spanned by the axial guide direction and the radial feed direction. Hereinafter, this orientation of the tool spindle is referred to as the dressing orientation. A defined selection of the dressing orientation 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, relative to the dressing tool by moving the grinding worm along the inclined axial guide direction in order to dress the grinding worm across its entire width. An axial carriage can be used for this purpose. If the tool spindle is mounted on a shift carriage, a shift carriage can be used alternatively or additionally depending on the embodiment.

[0034] The dressing device may comprise a dressing spindle designed to drive the dressing tool in rotation about the dressing spindle axis. The dressing spindle is preferably configured to pivot about at least one pivot axis so as to engage the dressing tool with the machining tool when the tool spindle is in the above-mentioned dressing orientation. For this purpose, the dressing device may comprise a corresponding pivot body. The pivot axis of the dressing spindle is preferably transverse to the axial feed direction, in particular at an angle of 60° to 120° to the axial feed direction, and transverse to the workpiece axis, preferably at an angle of 60° to 120° to the workpiece axis, in particular perpendicular to the workpiece axis. If the workpiece axis is spatially vertical, the pivot axis of the dressing spindle is preferably horizontal.

[0035] The dressing device may be mounted on a movable tool carrier together with at least one work spindle or may be arranged fixedly relative to the machine bed.

[0036] The present invention also provides a computer program comprising instructions for causing a machine tool controller of the type described above, in particular one or more processors of the controller, to carry out the processes described above. The computer program may be stored in a suitable memory device.

[0037] Furthermore, the present invention provides a computer-readable medium on which the computer program is stored, which may be a non-volatile medium such as a flash memory, a CD, a hard disk, etc.

[0038] Preferred embodiments of the present invention are described below with reference to the drawings, which are for illustrative purposes and are not to be construed as limiting. [Brief explanation of the drawings]

[0039] [Figure 1] FIG. 1 is a schematic perspective view of a generating gear grinding machine according to a first embodiment. [Figure 2] FIG. 2 is a schematic side view of the generating gear grinding machine of FIG. 1. [Figure 3] FIG. 1 is a diagram illustrating coordinate transformation during machining of a cylindrical gear. [Figure 4] FIG. 1 is a schematic side view of a cylindrical gear having teeth modified by crowning. [Figure 5] FIG. 5 is a diagram showing coordinate transformation when machining the cylindrical gear according to FIG. 4. [Figure 6] FIG. 10 is a schematic block diagram of the functional unit controlling the axial feed movement. [Figure 7] FIG. 10 is a schematic side view of a generating gear grinding machine according to a second embodiment. [Figure 8] FIG. 10 is a schematic side view of a generating gear grinding machine according to a third embodiment. [Figure 9] FIG. 10 is a schematic side view of a generating gear grinding machine according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0040] <Example structure of a generating gear grinding machine> 1 and 2 show a first embodiment of a generating gear grinding machine 1 as an example of a machine tool for machining gears. The machine comprises a machine bed 4, on which a tool carrier 5 is guided by linear guides 6 along a radial infeed direction X. The tool carrier 5 carries an axial carriage 7, which is displaceably guided relative to the tool carrier 5 along an axial guide direction Z'. A grinding head 9 is attached to the axial carriage 7 and can pivot about a pivot axis A extending 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 carriage, which is arranged so that a tool spindle 11 moves along a shift direction Y. The shift direction Y extends perpendicular to the pivot axis A and thus perpendicular to the X direction, but not necessarily perpendicular to the Z' direction. A finishing tool in the form of a worm-shaped 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 extends parallel to the Y direction.

[0041] The machine bed 4 also carries a swiveling workpiece carrier 15 in the form of a turret, which can swivel 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 workpiece spindle 16, shown on the left in FIG. 2, is in the machining position, in which a workpiece 18 clamped on it can be machined by the grinding worm 12. For this purpose, this workpiece spindle drives the workpiece 18 to rotate about a vertical first workpiece axis C1. The other workpiece spindle 17 is offset by 180° and is in a workpiece exchange position. In this position, the 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.

[0042] Additionally, mounted on the turret is a dressing device 13 (shown only diagrammatically) having a dressing tool 14. The dressing device 13 serves to dress the grinding worm 12.

[0043] All driven linear and rotary axes of the gear grinding machine 1 are digitally controlled by a machine controller having an operator panel 2 and axis modules 3. Each axis module 3 provides at its output a control signal for one machine axis (i.e. for at least one actuator, such as a servo motor, used to drive the associated machine axis).

[0044] <Workpiece machining> To machine an unmachined, pre-toothed workpiece (blank) 19, the workpiece 19 is clamped by an automatic workpiece changer on the workpiece spindle 17 in the workpiece change position. The workpiece is changed during the machining of another workpiece 18 on the other workpiece spindle 16 in the machining position. When the new workpiece 19 to be machined is clamped and machining of the other workpiece 18 is completed, the workpiece carrier 15 is swiveled 180° about the C3 axis, so that the spindle with the new workpiece to be machined reaches the machining position. Before and / or during the swiveling operation, a meshing operation is performed by a meshing probe. The meshing probe is arranged on the workpiece carrier 15, not shown. For this purpose, the workpiece spindle 17 is set in a rotating state, and the position of the tooth space of the workpiece 19 is measured by the meshing probe. Based on this, the rotation angle is set.

[0045] When the work spindle 17 carrying the workpiece 19 to be machined reaches the machining position, the workpiece 19 is engaged with the grinding worm 12 by moving the tool carrier 5 along the X axis. At this point, the workpiece 19 is machined by the rotating grinding worm 12 in rolling engagement. The machine performs 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 performs a movement along the Z' axis, but at a speed that does not change sign.

[0046] In parallel with the machining of the workpiece, the finished workpiece 18 is removed from the other work spindle 16 and another blank is clamped onto this spindle.

[0047] <Axial direction> In addition to the previously mentioned directions X, Y and Z', a further direction Z is defined. By definition, this direction is parallel to the workpiece axis C1, i.e. parallel to the axis of rotation of the workpiece in the machining position. A machining stroke along the Z' axis continuously changes the position of the tool relative to the workpiece along the Z direction when machining the workpiece in order to machine teeth across the entire width of the workpiece. This is called the axial feed, and therefore the Z direction is also called the axial feed direction.

[0048] In the prior art, the axial guide direction Z', i.e., the direction in which the axial carriage 7 is displaceably guided, usually coincides with the axial feed direction Z. However, in the present machine, these directions differ from each other. Specifically, the Z' direction extends in a plane spanning the X and Z directions, at an angle ψ to the Z direction. The absolute value of ψ is between 0.1° and 30°, in particular between 0.1° and 30°, preferably between 0.1° and 15°. A relatively small angle may be sufficient, for example between 0.1° and 3°, in particular between 0.5° and 3°.

[0049] For the currently proposed arrangement in the directions X, Y, Z, Z', A, B and C1, the following relationships hold:

number

[0050]

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[0051] <Coordinate conversion> The machine controller typically calculates, for a desired tooth profile, the corresponding control commands in the coordinate system X, Y, Z. In the present machine, a pure feed movement along the Z direction requires simultaneous movements along the X and Z' directions. In order to be able to operate the machine without having to rewrite all the machine programs, the machine control device is advantageously designed to convert normal feed commands for movements along the Z direction into control commands for simultaneous movements along the X and Z' directions.

[0052] This is explained below with reference to Figure 3. The tool moves along the Z direction at a constant velocity v Z It is assumed that the workpiece is moved from an initial position with coordinates x=x0, z=z0 to an end position with coordinates x=x0, z=z1 at a constant center distance relative to the workpiece. The corresponding movement profile 31 is shown in Figure 3(a). Such a movement profile is chosen when cylindrical gears are to be machined without flank modification by further axial movements.

[0053] To generate such a movement profile in the present machine, the drives must be operated simultaneously along the X and Z' directions. This is shown in Figure 3(b). As can be seen from this figure, in order to compensate for the tilt of the axial guiding direction Z', the axial carriage 7 moves continuously along the positive Z' direction, while the tool carrier 5 moves continuously in the negative X direction (i.e. to the right in Figure 2). Overall, Axial carriage 7 moves at a constant speed along the Z' direction from position z'0 to position z'1, and at the same time moves at a constant speed along the X direction from position x0 to position x1. The following holds for the start and end positions: z'1-z'0=(z1-z0) / cosψ x1-x0=-(z1-z0) tanψ

[0054] Therefore, the velocity v' along the Z' direction Z and v along the X direction X The following holds for v' Z =v Z / cosψ v X =-v Z tanψ

[0055] The corresponding movement profile 31' along the X and Z' directions is shown in FIG.

[0056] Based on this, it is easily possible to convert feed commands along the Z direction into converted feed commands along the X and Z' directions.

[0057] If the tool simultaneously makes a shift movement along the Y axis, this movement is not affected by a transformation to the X, Y, Z' coordinate system, nor by a tilting movement about the A axis, as occurs for example during machining, or by a change in the rolling angle to produce a further rotational movement between the workpiece and the tool.

[0058] Assuming that the coordinate origin in the Z direction and the coordinate origin in the Z' direction are the same, the spatial coordinates x, y, z in the coordinate system X, Y, Z can be transformed into spatial coordinates x', y', z' in the coordinate system X, Y, Z' as follows: x'=xz·tanψ y'=y z'=z / cosψ

[0059] When measured by measurement systems arranged along the X and Z' directions, the inverse transformation T -1 is applied and based on such measurements, Axial carriage 7The X and Z coordinates of the coordinate system X,Y,Z are determined. This inverse transformation may be necessary to provide the machine control with the measured coordinates in the required form. In this case, from the coordinates x', y', z' in the coordinate system X,Y,Z', the coordinates x, y, z in the coordinate system X,Y,Z are calculated as follows: x=x'+z'·sinψ y=y' z=z'·cosψ

[0060] <Creating corrections by crowning> In the following, the production of a modification by crowning in a cylindrical gear will be explained with reference to FIGS.

[0061] A modified cylindrical gear 32 that is crowned along its width is shown diagrammatically in Figure 4. The teeth of the cylindrical gear are thicker at the center than at the ends along the width direction (this is the Z direction when machining), and the tooth flanks have a correspondingly curved ridge. Sometimes, for production reasons, the tip diameter is also larger at the center than at the ends of the gear, so that the gear also has a barrel-shaped profile. In Figure 4, the barrel profile has been greatly exaggerated to more easily explain the principle. In reality, such modifications are usually only in the range of a few micrometers and are not visible to the naked eye.

[0062] From the prior art it is known to produce crowned cylindrical gears by superimposing a slow radial infeed movement in the X direction on a feed movement along the Z direction. Such a movement profile 33 is shown in Figure 5(a). A uniform axial feed movement at constant speed along the Z direction is superimposed on an infeed movement along the X direction. The infeed movement initially has a positive velocity (coordinate x increases), which decreases until the infeed speed at the center of the gear width becomes zero and changes sign (i.e. coordinate x decreases again).

[0063] Very slow radial infeed rates are problematic due to the unavoidable effects of friction, as is the reversal of the direction of the infeed movement, since the elements involved in guiding along the X direction exhibit unavoidable reversal effects.

[0064] For this machine, a reversal of the infeed movement direction is avoided when generating the modification, and the infeed speed never drops below a predetermined minimum speed when machining the tooth, provided that the crowning requirement is not too great. This is shown in FIG. 5(b), which shows the resulting movement profile 33'. The tool carrier 5 moves continuously in the negative X direction to compensate for the tilt in the Z' direction. This continuous basic movement is superimposed with a movement to generate the modification. However, the speed of the superimposed movement is always less than the speed of the basic movement, so that the direction never changes when machining the tooth and the infeed speed never drops below a predetermined minimum speed.

[0065] <Function unit that controls axial feed movement and radial feed movement> 6 shows schematically the various functional units used to generate the axial feed movement along the Z direction and the radial feed movement along the X direction. Position sensors 41, 42 are Axial Carriage The first transform device 43 detects the positions x', z' of the 7. -1 The control computer 44 converts these positions in the coordinate system X, Y, Z' into positions x and z in the coordinate system X, Y, Z by applying Axial Carriage 7. A second transformation device 45 transforms these control signals into transformed control signals Ax', Az' in the coordinate system X, Y, Z' and forwards these transformed control signals to the axis module 3 of the machine controller.

[0066] <Uses when dressing> From the prior art, it is known to make modifications to the flank of the grinding worm during dressing by a corresponding axial movement in order to transfer these modifications to the workpiece flank during subsequent machining in a diagonal manner, and for this purpose it is known to engage a spatially fixed dressing device with a rotating dressing wheel with the grinding worm, which generates the required movements in relation to the machine axes X and Y.

[0067] Different dressing strategies are possible for the machine, in which the grinding worm pivots about the A axis so that the shift axis Y and the tool axis B are vertical, i.e. extend along the Z direction. The dressing device is also aligned accordingly.

[0068] FIG. 2 shows the dressing device 13, but only diagrammatically, using dashed lines. The dressing device is mounted on a workpiece carrier (turret) 15. By rotating the turret 90°, the dressing device can be moved to a position opposite the grinding worm 12. The dressing device 13 comprises a dressing spindle on which a dressing wheel 14 is mounted and which is driven to rotate. The dressing spindle is mounted on a swivel 21. The swivel is connected to the workpiece carrier and can be swiveled so that the dressing wheel 14 can be aligned with the grinding worm profile in the direction of the worm thread. The corresponding swivel axes extend horizontally in space, perpendicular to the respective workpiece axes C1 and C2. In FIG. 2, the corresponding swivel axes extend perpendicularly to the drawing plane. In addition, the dressing spindle can swivel about a further swivel axis that also extends horizontally in space and perpendicular to the above-mentioned swivel axis. In Figure 2, this further pivot axis extends horizontally in the drawing plane. This further pivot axis can be used, for example, to change the profile angle during dressing.

[0069] At this point, the required dressing movement along the tool axis B is generated by the axial carriage 7, rather than by a shift carriage along the Y axis as is customary. Similar considerations apply here as discussed above for workpiece machining. In particular, in this way it is possible to avoid a reversal of direction along the X direction when the modification is generated on the grinding worm flank.

[0070] Likewise, the invention is advantageous when dressing is carried out by means of a gear-shaped dressing wheel clamped to the work spindle.

[0071] <Further uses> The advantages of the present invention have been explained above using the example of the production of crowned cylindrical gears. However, the present invention is not limited to this application and can be advantageously used in the production of other teeth or gears. In particular, the present invention is also advantageous in the production of teeth that have been modified in other ways, for example teeth that have been modified conically, since the present invention can be used there as well to avoid problematic friction effects.

[0072] <Second embodiment> FIG. 7 shows a schematic diagram of a generating gear grinding machine according to a second embodiment. This embodiment differs from the first embodiment in that the A axis is not perpendicular to the Z direction and not parallel to the X direction, but perpendicular to the Z' direction and accordingly at an angle ψ with respect to the X direction. This means that as soon as the swivel angle about the A axis deviates from the position shown in FIG. 7, the Y axis and the tool axis B are no longer perpendicular to the X direction. Nevertheless, the advantages mentioned above can still be achieved with this arrangement. This embodiment is particularly suitable for small tilting angles of 0.1° to 3°.

[0073] Generally, in this embodiment, the following applies to the arrangement in the directions X, Y, Z, Z', A, B and C1.

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[0074] Due to the tilted A-axis, an additional coordinate transformation is required compared to the first embodiment in order to go from the coordinate system defined by the machine axes X, Y, Z', A, B, C1 to a Cartesian coordinate system or to the conventional coordinate system of the machine controller and vice versa. However, the corresponding transformation can be easily derived by simple trigonometric considerations.

[0075] <Third embodiment> 8 shows a schematic representation of a generating gear grinding machine according to a third embodiment. In this embodiment, the entire tool carrier 5, including the axial carriage 7, the shift carriage and the grinding head 9, is constructed conventionally. In particular, the axial guide direction Z' is perpendicular to the feed direction X. Instead, the workpiece carrier (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, is no longer perpendicular to the X direction.

[0076] Again in this embodiment, further coordinate transformations are required compared to the first embodiment to go from the coordinate system defined by the machine axes X, Y, Z', A, B, C1 to a Cartesian coordinate system or to the conventional coordinate system of the machine controller and vice versa. Again, the corresponding transformations can be easily derived by simple trigonometric considerations.

[0077] <Fourth embodiment> FIG. 9 shows a schematic diagram of a generating gear grinding machine according to a fourth embodiment. Similar to the first and second embodiments, the turret, having axes C1 and C3, is positioned vertically in space, and the axial carriage 7 is guided relative to the tool carrier 5 along an axial guide direction Z'. The axial guide direction Z' is inclined with respect to the axis C1, which extends vertically in space, by an inclination angle ψ relative to the vertical. However, unlike the first and second embodiments, the entire tool carrier 5, including the axial carriage 7, shift carriage, and grinding head 9, is not guided strictly horizontally on the machine bed 4, but is guided along a direction inclined horizontally by the inclination angle ψ. Similar to the embodiments discussed above, the guide direction is again referred to as the X direction. Therefore, the X direction here is not perpendicular to the Z direction, but rather perpendicular to the Z' direction. Similar to the first embodiment, the A axis is horizontal in space and therefore perpendicular to the Z direction. Due to the inclined X axis, the A axis is not parallel to the X direction.

[0078] Generally, in this embodiment, the following applies to the arrangement in the directions X, Y, Z, Z', A, B and C1.

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[0079] Again in this embodiment, further coordinate transformations are required compared to the first embodiment to go from the coordinate system defined by the machine axes X, Y, Z', A, B, C1 to a Cartesian coordinate system or to the conventional coordinate system of the machine controller and vice versa. Again, the corresponding transformations can be easily derived by simple trigonometric considerations.

[0080] <Modification> In the example discussed above, the tilt angle ψ is positive, i.e., the Z' axis is tilted in the positive X direction, away from the workpiece axis C1. However, this angle can also be negative. The mentioned transformation remains valid in this situation. A negative tilt angle ψ can be particularly advantageous if the final finishing stroke is along the negative Z direction (i.e., from top to bottom in Figure 2), because in this case the tool carrier 5 moves along the negative X direction, i.e., towards the workpiece, to generate a compensating movement. This is advantageous because in this way the radial machining forces cancel out the compensating movement, resulting in defined force conditions in the components involved in generating the X movement.

[0081] The present invention is not limited to specific machining methods. The advantages of the present invention have been described above with reference to continuous generating grinding. However, the present invention also shows advantages in other gear manufacturing processes, including processes using geometrically undefined cutting edges as well as processes using geometrically defined cutting edges. Examples of such processes are part generating grinding, discontinuous or continuous form grinding, gear honing, gear hobbing, or hob peeling (gear skiving). The present invention can be used in the production of both externally and internally toothed workpieces. The present invention is particularly advantageous in the micromachining (finishing), especially hard micromachining, of pre-toothed workpieces.

[0082] The invention is not limited to a specific machine axis sequence: depending on the type of machine, it may be advantageous to arrange the axial carriage directly on the machine bed and the work spindle on the radial carriage, for example, in order to realize radial infeed by moving the work spindle.

[0083] The present invention is not limited to the situation where the radial infeed direction X is perpendicular to the workpiece axis C1. For example, in the third and fourth embodiments, the radial infeed direction X extends at an angle different from the workpiece axis C1 by 90°. However, in this situation, it is also advantageous if the axial guiding direction Z' lies in a common plane with the radial infeed direction X and the workpiece axis C1.

[0084] Instead of two work spindles, there can be three or more work spindles, or even a single work spindle. At least one work spindle does not have to be arranged on a movable workpiece carrier, but can be mounted directly on the machine bed. In another embodiment, at least one work spindle is arranged on a movable workpiece carrier, realizing a radial infeed movement along the X direction. Also, the A axis can be realized on the workpiece side instead of the tool side.

[0085] The dressing device 13 may be mounted on the machine bed rather than on the movable workpiece carrier, in which case the tool carrier 5 may be configured to pivot relative to the machine bed in order to move the machining tool to the dressing tool, as for example in U.S. Pat. No. 5,857,894.

[0086] From the above, it can be seen that there are a great many possible relative configurations of the axes involved, and the invention is not limited to any particular configuration.

[0087] Furthermore, the present invention is not limited to a particular type of drive for the various linear guides: the drive can be operated in any manner known in the art, for example by a ball screw drive or a linear motor.

Claims

1. A machine tool (1) for machining gears, comprising: a work spindle (16) that rotates a work (18) around a work axis (C1); a tool spindle (11) for driving a tool (12) to rotate around a tool axis (B); an axial carriage (7) configured to change the relative axial feed position between the tool spindle (11) and the work spindle (16) with respect to the work axis (C1); Equipped with the axial carriage (7) is guided along an axial guiding direction (Z') inclined to the work axis (C1) by an inclination angle (ψ), the inclination angle (ψ) having an absolute value between 0.1° and 30°; a feed carriage (5) configured to vary the radial distance between the tool axis (B) and the workpiece axis (C1) along a radial feed direction (X), the axial guide direction (Z') extending in a common plane of the workpiece axis (C1) and the radial feed direction (X); a control device (2, 3) configured to control the machine tool (1); The control device (2, 3) a tool (12) clamped to the tool spindle (11) is configured for simultaneous movement between the tool spindle (11) and the work spindle (16) along the axial guide direction (Z') and the radial feed direction (X) while the tool (12) clamped to the tool spindle (11) is in machining engagement with the workpiece (18) clamped to the work spindle; the movement along the axial guiding direction (Z') is performed at an axial guiding speed, and the movement along the radial infeed direction (X) is performed at a radial infeed speed; A machine tool, wherein the radial infeed rate does not change sign during a machining stroke, and wherein the radial infeed rate during a machining stroke does not fall below a threshold value corresponding to a predetermined minimum rate.

2. 2. The machine tool (1) according to claim 1, wherein the tilt angle (ψ) has an absolute value between 0.5° and 30°.

3. 3. A machine tool according to claim 1 or 2, wherein the radial infeed direction (X) extends at an angle of 60° to 120° relative to the workpiece axis (C1).

4. 3. A machine tool according to claim 1 or 2, wherein the radial infeed direction (X) is perpendicular to the workpiece axis (C1).

5. A machine tool (1) according to any one of claims 1 to 4, A machine bed (4), the feed carriage (5) is guided on the machine bed (4) so ​​as to be displaceable along the radial feed direction (X) and constitutes a tool carrier; The machine tool, wherein said axial carriage (7) is guided on said feed carriage (5) along said axial guiding direction (Z').

6. 6. The machine tool (1) according to any one of claims 1 to 5, wherein the tool spindle (11) is swivelable relative to the axial carriage (7) about a pivot axis (A), the pivot axis (A) extending in a common plane with the workpiece axis (C1) and the radial feed direction (X) at an angle with respect to the radial feed direction (X) having an absolute value between 0° and 30°.

7. 7. The machine tool (1) according to claim 6, wherein the tool spindle (11) is displaceable relative to the axial carriage (7) along a shift direction (Y) extending parallel to the tool axis (B), the shift direction (Y) extending perpendicular to the pivot axis (A).

8. 8. The machine tool (1) according to any one of claims 1 to 7, wherein the control device (2, 3) is configured to control the radial infeed rate and the axial guiding rate such that they have a ratio that varies during a machining stroke.

9. 9. The machine tool (1) according to any one of claims 1 to 8, wherein the control device (2, 3) is configured to control the radial infeed rate in such a way that the resulting movement between the tool spindle (11) and the work spindle (16) along the radial infeed direction (X) changes its sign during a machining stroke (v Ｘ ) a radial feed rate and an axial guiding rate are controlled to have a predetermined value.

10. A machine tool (1) according to any one of claims 1 to 9, wherein the control device (2, 3) a first transformation device (43) for transforming position variables (x', z') measured along the radial feed direction (X) and the axial guide direction (Z') into transformed position variables (x, z) along the radial feed direction (X) and an axial feed direction (Z) parallel to the workpiece axis (C1); a second conversion device (45) for converting control commands for the movement of the tool spindle (11) relative to the work spindle (16) along an axial feed direction (Z) parallel to the work axis (C1) into converted control commands (Ax', Az') for the simultaneous movement of the tool spindle (11) along the axial guiding direction (Z') and the radial feed direction (X); A machine tool comprising at least one of the following:

11. A machine tool (1) for machining gears, comprising: a work spindle (16) that rotates a work (18) around a work axis (C1); a tool spindle (11) for driving a tool (12) to rotate around a tool axis (B); an axial carriage (7) configured to change the relative axial feed position between the tool spindle (11) and the work spindle (16) with respect to the work axis (C1); Equipped with the axial carriage (7) is guided along an axial guiding direction (Z') inclined to the work axis (C1) by an inclination angle (ψ), the inclination angle (ψ) having an absolute value between 0.1° and 30°; a feed carriage (5) configured to vary the radial distance between the tool axis (B) and the workpiece axis (C1) along a radial feed direction (X), the axial guide direction (Z') extending in a common plane of the workpiece axis (C1) and the radial feed direction (X); a dressing device (13) comprising a dressing tool (14); a control device (2, 3) configured for simultaneous movement between the tool spindle (11) and the work spindle (16) along the axial guiding direction (Z') and the radial infeed direction (X), the control device (2, 3) is configured to translate the tool spindle (11) into a dressing orientation in which the tool axis (B) is in a plane subtended by the axial guiding direction (Z') and the radial feed direction (X) or parallel to said plane, and to dress the tool (12) with the dressing tool (14) while causing a simultaneous movement along the axial guiding direction (Z') and the radial feed direction (X), the movement along the axial guiding direction (Z') is performed at an axial guiding speed, and the movement along the radial infeed direction (X) is performed at a radial infeed speed; The radial feed rate does not change sign during dressing, and the radial feed rate during dressing does not fall below a threshold value corresponding to a predetermined minimum speed.

12. 12. The machine tool (1) according to claim 11, wherein the dressing device (13) comprises a dressing spindle configured to drive in rotation the dressing tool (14) about a dressing spindle axis, the dressing spindle being swivelable about at least one dressing pivot 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, the dressing pivot axis extending at an angle of 60° to 120° with respect to the axial guiding direction (Z').

13. 11. The machine tool (1) according to any one of claims 1 to 10, configured to perform one of the processes of continuous generating grinding, part generating grinding, discontinuous or continuous form grinding, gear honing, hobbing or hob peeling.

14. A method for machining tooth flanks of a workpiece (18) using a machine tool (1) according to any one of claims 1 to 10, comprising the steps of: a simultaneous movement between the tool spindle (11) and the work spindle (16) along the axial guiding 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 work spindle, wherein the movement along the axial guiding direction (Z') is performed at an axial guiding speed and the movement along the radial infeed direction (X) is performed at a radial infeed speed; A method wherein the radial feed rate has a sign that does not change during a machining stroke and an absolute value that does not fall below a threshold value corresponding to a predetermined minimum rate during a machining stroke.

15. The radial feed rate is the rate at which the resulting movement between the tool spindle (11) and the work spindle (16) along the radial feed direction (X) changes its sign during a machining stroke (v Ｘ 15. The method of claim 14, wherein the radial feed rate and the axial guide rate have a time-varying ratio such that:

16. 13. A method for dressing a tool (12) for machining gears using a machine according to claim 11 or 12, comprising the steps of: generating a relative movement between the tool (12) and the dressing device (13) along the inclined axial guide direction (Z') while the tool (12) is engaged with a dressing tool (14) that dresses the tool (12); 10. The method of claim 9, wherein, before dressing, the tool spindle (11) is translated into a dressing orientation in which the tool axis (B) extends in a plane spanned by the axial guiding direction (Z') and the radial feed direction (X) or parallel to said plane.

17. The dressing device (13) comprises a dressing spindle configured to drive the dressing tool (14) in rotation about a dressing spindle axis, and the method comprises the steps of:

17. The method according to claim 16, comprising pivoting the dressing spindle (11) about at least one dressing pivot axis to engage the dressing tool (14) with the tool (12) when the tool spindle (11) is in the dressing orientation, the dressing pivot axis extending transversely to the axial guiding direction (Z').

18. measuring position variables (x', z') along the radial feed direction (X) and the inclined axial guide direction (Z'); Transforming the measured position variables (x', z') into transformed position variables (x, z) along the radial feed direction (X) and an axial feed direction (Z) extending parallel to the workpiece axis (C1); The method according to any one of claims 14 to 17, comprising:

19. generating control commands (Ax, Az) for movement of the tool spindle (11) relative to the work spindle (16) along an axial feed direction (Z) extending parallel to the work axis (C1); - converting the generated control commands into converted control commands (Ax', Az') for simultaneous movements of the tool spindle (11) along the axial guiding direction (Z') and the radial infeed direction (X); The method according to any one of claims 14 to 18, comprising:

20. 16. The method according to claim 14 or 15, wherein the method is one of continuous generating grinding, part generating grinding, discontinuous or continuous form grinding, gear honing, hobbing or hob peeling.

21. A computer program comprising instructions for causing a control device (2, 3) of a machine tool (1) according to any one of claims 1 to 13 to perform the method according to any one of claims 14 to 20.

22. 22. A computer readable medium having stored thereon the computer program of claim 21.

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