SPINDLE UNIT FOR A MACHINE TOOL FOR FINE-MACHINING WORKPIECES THAT HAVE GROOVED-SHAPED PROFILES

Abstract

A spindle unit for a machine tool for fine-machining workpieces having groove-shaped profiles, has a rotatably mounted spindle shaft (2). The spindle shaft is subdivided in the axial direction (AR), one behind the other, into a fastening portion (A) for fastening a tool (4) or a workpiece to be machined, a first bearing portion (B), a force transmission portion (C), and a second bearing portion (D). A drive unit (5) serves to drive the spindle shaft by way of force transmission onto the force transmission portion. A first and a second bearing point (13, 14) are designed to bear the spindle shaft in the first bearing portion, and a third bearing point (15) serves to mount the spindle shaft on the second bearing portion. The first and the second bearing points each have one or more hydrostatic bearings. The third bearing point has one or more hydrostatic and/or hydrodynamic bearings.

Claims

1. A spindle unit for a machine tool for fine-machining workpieces having groove-shaped profiles, comprising: a spindle shaft which is mounted to be rotatable about an axis of rotation and defines an axial direction and a radial direction with this axis of rotation, and which is divided successively in the axial direction into a mounting portion for attaching a tool or a workpiece to be machined, a first bearing portion, a force-transfer portion and a second bearing portion; a drive unit for driving the spindle shaft in a rotational movement about the axis of rotation by means of force transfer to the force-transfer portion; a first bearing point and a second bearing point for supporting the spindle shaft in the first bearing portion and a third bearing point for supporting the spindle shaft in the second bearing portion, wherein the first and the second bearing point each have one or more hydrostatic bearings and are each formed for absorbing both radial and axial forces, and wherein the third bearing point has one or more hydrostatic and/or hydrodynamic bearings and is formed for absorbing radial forces.

2. The spindle unit as claimed in claim 1, wherein the first and/or the second bearing point is conically formed.

3. The spindle unit as claimed in claim 2, wherein both the first and the second bearing point are conically formed and wherein the cones formed by these two bearing points are aligned in mutually opposite directions in relation to the axis of rotation.

4. The spindle unit as claimed in claim 2, wherein the cones formed by the first and/or by the second bearing point have an opening angle in a range of 10 to 60 in relation to the axis of rotation.

5. The spindle unit as claimed in claim 1, wherein the third bearing point is additionally formed for absorbing axial forces.

6. The spindle unit as claimed in claim 1, wherein the first bearing point has one or more first bearing pockets and the second bearing point has one or more second bearing pockets and wherein at least one first pressure controller is provided, which serves for controlling the pressure conditions prevailing in the first bearing pockets, and at least one second pressure controller is moreover provided, which serves for controlling the pressure conditions prevailing in the second bearing pockets and is formed separately in relation to the first pressure controller(s).

7. The spindle unit as claimed in claim 6, wherein a plurality of first bearing pockets and a plurality of second bearing pockets as well as a plurality of first pressure controllers and a plurality of second pressure controllers are present and wherein each of the first bearing pockets is associated with one of the first pressure controllers in each case and each of the second bearing pockets is associated with one of the second pressure controllers in each case.

8. The spindle unit as claimed in claim 6, wherein the third bearing point has a hydrostatic bearing having one or more third bearing pockets and wherein at least one third pressure controller is provided, which serves for controlling the pressure conditions prevailing in the third bearing pockets and is formed separately in relation to the first pressure controller(s) and the second pressure controller(s).

9. The spindle unit as claimed in claim 8, wherein a plurality of third bearing pockets as well as a plurality of third pressure controllers are present and wherein each of the third bearing pockets is associated with one of the third pressure controllers in each case.

10. The spindle unit as claimed in claim 6, wherein the first pressure controller(s) and the second pressure controller(s) are each formed as progressive flow controllers.

11. The spindle unit as claimed in claim 6, wherein the first pressure controller(s), and the second pressure controller(s) each have a compact construction and wherein the corresponding pressure controls take place by means of capillaries and/or throttles and/or restrictors and/or by means of an electronic control.

12. The spindle unit as claimed in claim 6, wherein the first pressure controller(s) are each arranged substantially at the same height as the first bearing point relative to the axial direction, and wherein the second pressure controller(s) are each arranged at substantially the same height as the second bearing point relative to the axial direction.

13. The spindle unit as claimed in claim 6, wherein a mounting device is attached to the mounting portion of the spindle shaft for attaching a tool or a workpiece to be machined and wherein the first pressure controller(s) are arranged in the region of the mounting device along the axial direction.

14. The spindle unit as claimed in claim 1, wherein one or more fluid circuits are provided, which serve both for lubricating and also for cooling the first and the second bearing point.

15. The spindle unit as claimed in claim 1, additionally having at least one angle measuring device for detecting the rotational speed of the spindle shaft.

16. The spindle unit as claimed in claim 1, wherein sealing-air arrangements are provided to seal the bearing pockets of the first and the second bearing point, to the outside in the axial direction.

17. A machine tool having a spindle unit for fine-machining workpieces having groove-shaped profiles, the spindle unit comprising: a spindle shaft which is mounted to be rotatable about an axis of rotation and defines an axial direction and a radial direction with this axis of rotation, and which is divided successively in the axial direction into a mounting portion for attaching a tool or a workpiece to be machined, a first bearing portion, a force-transfer portion and a second bearing portion; a drive unit for driving the spindle shaft in a rotational movement about the axis of rotation by means of force transfer to the force-transfer portion; a first bearing point and a second bearing point for supporting the spindle shaft in the first bearing portion and a third bearing point for supporting the spindle shaft in the second bearing portion, wherein the first and the second bearing point each have one or more hydrostatic bearings and are each formed for absorbing both radial and axial forces, and wherein the third bearing point has one or more hydrostatic and/or hydrodynamic bearings and is formed for absorbing radial forces.

18. The spindle unit as claimed in claim 10, wherein the progressive flow controllers each have exclusively mechanical and/or hydraulic elements.

19. The spindle unit as claimed in claim 13, wherein the first pressure controller(s) are arranged within the mounting device in the radial direction.

20. The spindle unit as claimed in claim 14, wherein the one or more fluid circuits serve also for cooling the drive unit.

21. The spindle unit as claimed in claim 16, wherein the sealing-air arrangements are provided also to seal the bearing pockets of the third bearing point, to the outside in the axial direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Preferred embodiments of the invention are described below with reference to the drawings, which merely serve for explanation and are not to be interpreted as restrictive. The drawings show:

[0056] FIG. 1 a perspective view of an inventive spindle unit of a machine tool according to a first inventive embodiment;

[0057] FIG. 2 a central sectional view of a non-inventive spindle unit of a machine tool having a spindle shaft, which is radially mounted only in the first bearing portion (B), but not in the second bearing portion (D), to illustrate a possible characteristic bending behavior of the spindle shaft;

[0058] FIG. 3 a central sectional view of the spindle unit of FIG. 1 having a spindle shaft which is radially mounted both in the first bearing portion (B) and in the second bearing portion (D) to illustrate a possible bending behavior of the spindle shaft;

[0059] FIG. 4a a central sectional view through the spindle unit of FIG. 1;

[0060] FIG. 4b a perspective view of the spindle unit of FIG. 1, cut away centrally along its axis of rotation, without a spindle shaft;

[0061] FIG. 4c a sectional view through the plane I-I indicated in FIG. 4a;

[0062] FIG. 4d a sectional view through the plane II-II indicated in FIG. 4a;

[0063] FIG. 4e a sectional view through the plane III-III indicated in FIG. 4a;

[0064] FIG. 5 a central sectional view through a spindle unit of a machine tool according to a second inventive embodiment;

[0065] FIG. 6 a central sectional view through a spindle unit of a machine tool according to a third inventive embodiment;

[0066] FIG. 7 a central sectional view through a spindle unit of a machine tool according to a fourth inventive embodiment;

[0067] FIG. 8 the diagram of an exemplary fluid circuit for lubricating the bearing points of an inventive spindle unit of a machine tool; and

[0068] FIG. 9 a detailed view of the diagram of FIG. 8 in the region of the spindle shaft.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0069] FIGS. 1 to 7 show different embodiments of the spindle units of machine tools for fine-machining workpieces having groove-shaped profiles. Similar-acting elements are each denoted by the same reference signs in the different embodiments.

[0070] The spindle units shown in FIGS. 1 to 7 each have a spindle shaft 2 with a grinding tool 4 attached thereto. The spindle shafts shown in FIGS. 1 to 7 are therefore tool spindles for use in machine tools, in particular such as gear grinding machines.

[0071] FIG. 1 shows a perspective view of an inventive spindle unit of a machine tool having a housing 1 and a spindle shaft 2 rotatably supported therein. A grinding tool 4 is attached to the spindle shaft 2 in the region of its first end. The grinding tool 4 can be in particular a worm grinding wheel such as that used for grinding gears.

[0072] FIGS. 2 and 3 each illustrate, in a schematic sectional central view, one of several possible characteristic bending behaviors of the spindle shaft 2 which, in the gear grinding machine shown by way of example in FIG. 2, is only mounted in the first bearing portion B at the two bearing points 13 and 14 and, in the gear grinding machine shown by way of example in FIG. 3, has an additional bearing at a third bearing point 15. For illustrative purposes, some elements of the spindle unit are omitted in each case in FIGS. 2 and 3, for example the housing and the drive unit. Likewise for illustrative purposes, the bending behavior of the spindle shaft 2 in FIGS. 1 and 2 is shown greatly exaggerated in each case. This bending behavior has also been illustrated schematically. It is known to the person skilled in the art that the bending behavior can vary very greatly depending on the rotational speed or rotational frequency.

[0073] The spindle shafts 2 shown in FIGS. 2 and 3 each have a mounting portion A on which a mounting device in the form of a grinding tool flange 3 with a grinding tool 4 attached thereto is arranged. In FIGS. 2 to 7, the grinding tool 4 is mounted on the spindle shaft 2, in each case by way of example, by means of a grinding tool flange 3. It is also conceivable to mount the grinding tool 4 on the spindle shaft 2 directly (without a grinding tool flange 3). The cylindrically illustrated grinding tool 4 (or the truing tool and/or the workpiece, respectively) can furthermore also be disk shaped. In a force-transfer portion C, the spindle shaft 2 is set in rotation about the axis of rotation RA by means of a drive unit not shown here. Between the mounting portion A and the force-transfer portion C, the spindle shafts 2 shown in the FIGS. 2 and 3 each have a first bearing portion B having the two bearing points 13 and 14. The third bearing point 15, which is additionally provided in the case of the spindle shaft 2 shown in FIG. 3, is arranged in a second bearing portion D on the side of the force-transfer portion C which is opposite the first bearing portion B. The first and second bearing points 13 and 14 are each formed by a conically formed axial radial bearing; the third bearing point 15 by a cylindrical radial bearing.

[0074] At high rotational speeds of the spindle shaft 2 about the axis of rotation RA, the spindle shaft 2 tends, for various reasons, to vibrate and, accordingly, to bend. The longitudinal center line of the spindle shaft 2, which normally coincides with the axis of rotation RA in the idle state, then bends away from the axis of rotation RA in certain regions in the radial direction, as illustrated by the bending line BL in FIGS. 2 and 3.

[0075] In the non-inventive spindle unit of a machine tool, which is shown in FIG. 2, the spindle shaft 2 is only supported in the first bearing portion B at the two bearing points 13 and 14. In this case, the spindle shaft 2 bends strongly away from the axis of rotation RA with its longitudinal center line in each case in its end regions, i.e. in the region of the first spindle end 20 and in the region of the second spindle end 21. The bending-away of a region of the spindle shaft 2 from the axis of rotation RA becomes stronger the further away the region is from the next bearing point 13 or 14. The vibrating behavior of the spindle shaft 2 is therefore most pronounced in the regions of the first and second spindle end 20 and 21. This is unfavorable precisely because the first spindle end 20 is formed by the mounting portion A to which the grinding tool 4 is attached. The relatively strong vibrations of the first spindle end 20 are thus transferred directly to the grinding tool 4 and therefore impair the surface quality of the workpiece. The spindle end 21 on which, in most embodiments, an angle measuring device 19a (see FIG. 4a) is arranged behaves in the same way or, at certain frequencies/speeds, even more pronouncedly. The relatively strong vibrations also influence the grinding result since measuring errors can occur here.

[0076] With an additional radial bearing of the spindle shaft 2 in the second bearing portion D, as shown in FIG. 3, vibrations are prevented not only in the region of the second bearing portion D itself, which is of great significance for the angle measuring device 19a, but also in the mounting portion A. At high rotational speeds, the spindle shaft 2 is therefore bent less strongly overall and in particular in the region of the mounting portion A as well as in the second bearing portion D. The substantially reduced vibrations of the mounting portion A and the bearing portion D result in an improved grinding quality.

[0077] FIGS. 4a to 4d show an inventive exemplary embodiment of a spindle unit of a gear grinding machine having a spindle shaft 2, which is divided successively along the axis of rotation RA into a mounting portion A, a first bearing portion B, a force-transfer portion C and a second bearing portion D. The individual portions A, B, C and D adjoin one another directly here, without overlapping one another.

[0078] The axis of rotation RA corresponds to the longitudinal center axis of the spindle shaft 2. With its axis of rotation RA, the spindle shaft 2 defines an axial direction AR corresponding to the axis of rotation RA and a host of radial directions RR at a right angle thereto.

[0079] A stator unit 6 is connected to the housing 1 in a torsion-resistant manner. The stator unit 6 is part of a drive unit 5 in the form of an electric motor, which serves to drive the spindle shaft 2 in a rotational movement about its axis of rotation RA. A rotor unit 7, which likewise forms part of the drive unit 5, is attached to the spindle shaft 2, directly adjacent to the stator unit 6, in a torsion-resistant manner. The rotor unit 7 is formed here by a plurality of permanent magnets which are attached circumferentially to the outside of the spindle shaft 2. Whilst the spindle shaft 2 is radially surrounded by the rotor unit 7, the stator unit 6 surrounds the rotor unit 7. The spindle shaft 2, the rotor unit 7 and the stator unit 6 are arranged concentrically to one another. A cooling channel 25, or a plurality of cooling channels, is provided in the radial direction between the stator unit 6 and the housing 1 for conducting a coolant in order to dissipate the thermal energy produced during operation of the drive unit 5.

[0080] The force-transfer portion C of the spindle shaft 2 is defined by the arrangement of the drive unit 5 and in particular of the rotor unit 7 along the axis of rotation RA and extends in the axial direction AR at least from a first end 8 of the rotor unit 7 to a second end 9 of the rotor unit 7. During operation of the spindle unit, a drive force is transferred along the force-transfer portion C from the drive unit 5 to the spindle shaft 2, whereby the spindle shaft 2 is set in rotation about its axis of rotation RA.

[0081] In the region of the first spindle end 20, a grinding tool flange 3, which serves as a mounting device for the torsion-resistant attachment of a grinding tool 4, is attached to the mounting portion A of the spindle shaft 2. When the grinding tool 4 is mounted on the grinding tool flange 3, the spindle shaft 2 projects in the axial direction AR into or through a bore in the grinding tool 4. It is equally conceivable to mount a grinding tool in such a way that the spindle end does not project or only partly projects therethrough.

[0082] A first angle measuring device 19a for detecting the respective angular position of the spindle shaft 2 about its axis of rotation RA is provided by way of example at the second spindle end 21. A second angle measuring device 19b is likewise arranged by way of example on the first bearing portion B, directly adjacent to the mounting portion A, on the spindle shaft. With the aid of the angle measuring devices 19a and/or 19b, it is possible to ensure that the rotational speed of the spindle shaft 2 and therefore the grinding tool 4 corresponds as precisely as possible to the value specified by the control of the machine during the grinding procedure. The angle measuring devices can also be arranged at another point along the spindle axis, for example in the transition region from the first bearing portion B to the force-transfer portion C, and/or the arrangement of only one angle measuring device is also possible.

[0083] The spindle shaft 2 has a first, a second and a third bearing point 13, 14, 15 along the axial direction AR. The first bearing point 13 and the second bearing point 14 are each provided on a first fixed sleeve 26, which is attached to the housing 1 in a torsion-resistant manner. The third bearing point 15 is arranged on a second fixed sleeve 27, which is likewise attached to the housing 1 in a torsion-resistant manner.

[0084] The first bearing point 13 and the second bearing point 14 are arranged at a spacing from one another in the axial direction AR on the first bearing portion B, which extends between the grinding tool flange 3 and the rotor unit 7. To enable high rotational speeds and moreover to optimally damp possibly occurring vibrations, both the first bearing point 13 and the second bearing point 14 are each formed by a hydrostatic bearing. The bearings of the bearing points 13 and 14 are each conically formed and have a plurality (by way of example, 4 bearing pockets are illustrated in each case) of bearing pockets 13a, 13b, 13c, 13d, or 14a, 14b, 14c, 14d, respectively, (see FIGS. 4c and 4d) arranged at regular spacings about the spindle axis 2. In the axial direction AR, the bearing pockets 13a, 13b, 13c, 13d, or 14a, 14b, 14c, 14d, respectively, of the bearing points 13 and 14 are each sealed to the outside on both sides by means of sealing-air arrangements. Return channels for the fluid are generally located by way of example on both sides in the axial direction AR between the bearing points and the sealing-air arrangements.

[0085] The conical form of the first bearing point 13 and the second bearing point 14 determines that these are each arranged in a region of the spindle shaft 2 which tapers conically or widens conically, respectively, along the axial direction AR. In the present embodiment, the bearing of the first bearing point 13 tapers along the axial direction AR extending from the first spindle end 20 to the second spindle end 21. The bearing of the second bearing point 14, on the other hand, widens conically in the direction from the first spindle end 20 to the second spindle end 21. The cones formed by the bearings of the first and the second bearing point 13, 14 are therefore aligned with their opening angles along the axial direction AR in mutually opposite directions. The opening angles (see FIG. 4) of the bearings of the first and the second bearing point 13, 14, which are measured relative to the axis of rotation RA, are preferably each between 10 and 60. Owing to their conical design, the bearings of the bearing points 13 and 14 are each formed for absorbing forces acting both in the radial direction RR and in the axial direction AR.

[0086] The third bearing point 15 is formed by a cylindrical radial bearing, which is arranged on the second bearing portion D of the spindle shaft 2. The second bearing portion D extends in the axial direction AR from the force-transfer portion C to the second spindle end 21.

[0087] The bearing of the third bearing point 15 serves to stabilize the second spindle end 21 of the spindle shaft 2 in the radial direction RR. On the one hand, it is thus prevented that radial vibrations amplify in the region of the mounting device and thus impair the rotation of the grinding tool 4 and therefore the grinding quality. On the other hand, the bearing of the third bearing point 15 reduces measuring errors which occur as a consequence of the spindle bending at the second spindle end 21 and therefore near the angle measuring device 19a. During operation of the gear grinding machine, such measuring errors can lead to asynchronous rotational movements of the grinding tool 4 and the workpiece to be ground and therefore to an impaired grinding quality.

[0088] To enable relatively high rotational speeds of 3000 or even more revolutions per minute, the third bearing point 15 is also formed by a hydrostatic bearing. This has a plurality (by way of example, 4 bearing pockets are also illustrated here) of bearing pockets 15a, 15b, 15c, 15d, which are arranged at regular spacings about the spindle shaft 2 (see FIG. 4e), which is formed correspondingly cylindrically in the region of the third bearing 15. The bearing pockets 15a, 15b, 15c, 15d of the third bearing point 15 are also each sealed to the outside on both sides in the axial direction AR by means of sealing-air arrangements. Return channels for the fluid are generally located by way of example on both sides in the axial direction AR between the bearing points and the sealing-air arrangements. Instead of being formed by a hydrostatic bearing, the third bearing point 15 can also be formed by a hydrodynamic bearing.

[0089] The third bearing point 15 here is formed and arranged on the spindle shaft 2 in particular in such a way that movements of the spindle shaft 2 along the axial direction AR through the bearing of the third bearing point 15 are possible to a certain extent. Linear expansions of the spindle shaft 2, which are caused by a heating of the spindle shaft 2 during operation of the gear grinding machine, thus have no effect on the spindle bearing in the third bearing point 15. Although a temperature-related linear variation in the spindle shaft 2 results in a certain displacement of the spindle shaft 2 along the axial direction AR in the region of its second bearing portion D, it only results in a minimum displacement of the mounting portion A, and in particular the grinding tool 4, as a result of the first bearing point 13 and the second bearing point 14 moreover being arranged very close to one another and near to the grinding tool 4.

[0090] A plurality of first pressure controllers 16 are provided for controlling the hydrostatic pressure in the bearing of the first bearing point 13. Since, in each case, one of these first pressure controllers 16 is associated with, and connected to, each of the bearing pockets 13a, 13b, 13c, 13d belonging to the bearing of the first bearing point 13, the number of first pressure controllers 16 corresponds to the number of bearing pockets 13a, 13b, 13c, 13d belonging to the bearing of the bearing point 13. The same applies to the plurality of second pressure controllers 17 and the plurality of third pressure controllers 18, which serve for controlling the pressure conditions in the bearing pockets 14a, 14b, 14c, 14d, or 15a, 15b, 15c, 15d, respectively, of the bearings belonging to the second or third bearing point 14 or 15 respectively. In each case, one of the second pressure controllers 17 here is also associated with each of the bearing pockets 14a, 14b, 14c, 14d of the second bearing point 14 and in each case one of the third pressure controllers 18 is associated with each of the bearing pockets 15a, 15b, 15c, 15d of the third bearing point 15.

[0091] The first, second and third pressure controller 16, 17 and 18 each have a compact construction so that they can be accommodated in a housing which is closed to the outside. Each of the plurality of first, second and third pressure controllers 16, 17 and 18 is connected in each case via one pressure line to the correspondingly associated bearing pocket 13a, 13b, 13c, 13d, or 14a, 14b, 14c, 14d, or 15a, 15b, 15c, 15d, respectively, of the first, second or third bearing point 13, 14, and 15, respectively.

[0092] The first, second and third pressure controller 16, 17 and 18 are preferably each based exclusively on mechanical components, for example spring elements, and on hydraulic components, for example throttles. The pressure in the pressure- or bearing pockets 13a, 13b, 13c, 13d, or 14a, 14b, 14c, 14d, or 15a, 15b, 15c, 15d, respectively, can thus be controlled without electrical energy, which also dispenses with the need for corresponding wiring. The pressure controllers 16, 17 and 18 are advantageously formed according to one of the exemplary embodiments disclosed in EP 0 840 190 B1.

[0093] The plurality of first, second and third pressure controllers 16, 17 and 18 are each attached directly to a component of the spindle unit, which, in the radial direction RR, is arranged directly adjacent to that spindle shaft portion on which the bearing pocket 13a, 13b, 13c, 13d, or 14a, 14b, 14c, 14d, or 15a, 15b, 15c, 15d, respectively, connected to this pressure controller is located. The pressure controllers 16, 17 and 18 are each arranged approximately at the height of the corresponding bearing point 13, 14 or 15, respectively, along the axial direction AR. In the embodiment shown in FIGS. 4a-4e, the first pressure controllers 16 and the second pressure controllers 17 are each arranged at the first bearing portion B and, in particular, between the first bearing point 13 and the second bearing point 14 in the axial direction AR. The third pressure controllers 18, of which two can also be seen in FIG. 1, are located at the second bearing portion D.

[0094] The plurality of pressure controllers 16, 17 and 18 in each case and the individual bearing pockets 13a, 13b, 13c, 13d, or 14a, 14b, 14c, 14d, or 15a, 15b, 15c, 15d, respectively, of the first, second and third bearing point 13, 14 and 15 are connected to one another by means of a common fluid circuit, which cannot be seen in FIG. 4a but is shown in FIGS. 8 and 9 and described further below. A fluid circulates in the fluid circuit, which serves not only for controlling the pressure ratios prevailing in the individual bearing pockets but also for cooling and lubricating the first, second and third bearing point 13, 14 and 15. The same fluid can moreover be used for cooling the drive unit 5.

[0095] A further embodiment of an inventive spindle unit, which is illustrated by way of example on a gear grinding machine, is shown in FIG. 5. This embodiment of FIG. 5 corresponds substantially to the embodiment of FIG. 4, the difference being that the first bearing point 13 here is arranged at the same height as the grinding tool flange 3 along the axial direction AR and, if a grinding tool 4 is attached to said grinding tool flange, also at the same height as this grinding tool 4. The mounting portion A and the first bearing portion B therefore partly overlap here in the axial direction AR. Along the radial direction RR, the first bearing point 13 in the second embodiment is arranged here within the grinding tool flange 3 so that, if a grinding tool 4 is attached to the grinding tool flange 3, it is radially surrounded by this. The first pressure controllers 16 here are also arranged at the same point as the grinding tool flange 3 in the axial direction AR and therefore in the mounting portion A. If a cylindrical grinding tool 4 is attached to the grinding tool flange 3, the first pressure controllers 16, like the first bearing point 13, are located within the bore of the grinding tool 4. As in the embodiment of FIG. 4, the second bearing point 14 is arranged between the grinding tool flange 3 and the first rotor end 8 in the axial direction AR.

[0096] Since the first bearing point 13 is located within the mounting portion A and therefore directly in the region of the grinding tool flange 3, vibrations of the grinding tool 4 are optimally damped. Moreover, the spindle shaft 2 can thus have a smaller overall length and/or the spacing between the two bearings 13 and 14 can be increased.

[0097] The embodiment illustrated in FIG. 5 is suitable for grinding tools 4 from a certain bore diameter. However, the embodiment illustrated in FIGS. 4a-4e is more suitable for grinding tools 4 whereof the bore diameter is relatively small, since the first bearing point 13 and the first pressure controllers 16 there do not have to be accommodated within the bore of the grinding tool 4 but are arranged outside this. The embodiment of FIG. 4 is therefore particularly suitable for grinding tools which are formed for grinding at a very high circumferential speed and therefore have a large radial wall thickness.

[0098] In contrast to the embodiment shown in FIGS. 4a-4e, in the embodiment of FIG. 5 the second angle measuring device 19c is arranged by way of example directly adjoining the force-transfer portion C on the first bearing portion B.

[0099] A further embodiment of an inventive spindle unit of a gear grinding machine is shown in FIG. 6. This embodiment corresponds substantially to that of FIG. 5, although it could also be configured as in FIGS. 4a-4e, with the exception that an insert sleeve 22 is provided here, in which the spindle shaft 2 and the drive unit 5 are accommodated. A first sleeve support 23a serves for mounting the insert sleeve 22 in a receiving region provided accordingly on the housing 1. By way of example, the sleeve support 23a is a screw connection which is formed and arranged in such a way that both axial and also radial forces are transferred from the insert sleeve 22 to the housing 1 and can be absorbed by this latter. Along the axial direction AR, further sleeve supports are conceivable, which are preferably each located at the same height as the bearing points 14 and 15 and are formed such that the radial forces can be transferred to the housing 1. The sleeve supports 23b and 24 are illustrated by way of example in FIG. 6. The insert sleeve 22 has an external diameter which is approximately the same size as the internal diameter of the corresponding receiving region of the housing 1. The sleeve support 24 can be formed as a separate component, which is connected to the housing 1 by means of a screw connection for example, or it can be formed in one piece from the housing 1.

[0100] The inventive embodiment shown in FIG. 7 differs from that of FIGS. 4a-4e and also from that of FIGS. 5 and 6 in that the rotor unit 7 here is fixed on the outside of a holding sleeve 10, which is pushed onto the spindle shaft 2 and mounted thereon in a torsion-resistant manner. The rotor unit 7 can thus be attached to, or removed from, respectively, the spindle shaft very easily during assembly or for maintenance purposes, respectively. To enable the attachment of the holding sleeve 10, however, the external diameter of the spindle shaft 2 in the force-transfer portion C and in the second bearing portion D is somewhat smaller than that of the spindle shaft 2 shown in FIG. 4a.

[0101] An exemplary diagram of a fluid circuit for lubricating or supporting and cooling the bearing points 13, 14, 15 and for cooling the drive unit 5 is shown in FIGS. 8 and 9. The diagram shown in FIGS. 8 and 9 can be used in all embodiments according to FIGS. 1 to 7.

[0102] A common fluid reservoir 28, which serves for receiving the fluid, is integrated in the fluid circuit. The fluid received in the fluid reservoir 28 is used both for the hydrostatic bearing 13, 14 and 15 as a whole and for cooling the drive unit 5, which serves for driving the spindle shaft 2.

[0103] The fluid can be taken into a first fluid line 32a from the fluid reservoir 28 by means of a first and a second fluid pump 30 and 31, which are driven together by a drive motor or separately by a plurality (not illustrated) of drive motors 29. The first fluid line 32a branches into a second fluid line 32b and a third fluid line 32c.

[0104] The second fluid pump 31, which supplies the fluid under pressure to the first, second and third pressure controllers 16, 17, 18 in order to lubricate and cool them, is arranged within the second fluid line 32b. The first, second and third pressure controllers 16, 17 and 18 here are arranged parallel to one another in the fluid circuit.

[0105] The third fluid line 32c, within which the first fluid pump 30 is arranged, branches into a fourth fluid line 32d and a fifth fluid line 32e. The fourth fluid line 32d leads back to the branching point, where the first fluid line 32a leads into the second and the third fluid line 32b and 32c. The fourth fluid line 32d serves for the cooling and filtration of the fluid. A pre-tension valve 33 and a heat exchanger 34 are arranged in succession within the fourth fluid line 32d. The fluid arrives via the fifth fluid line 32e at the drive unit 5, through which fluid therefore flows parallel in relation to the pressure controllers 16, 17 and 18 for cooling purposes. From the pressure controllers 16, 17 and 18, the fluid arrives back in the fluid reservoir 28 via a sixth fluid line 32f.

[0106] Parallel thereto, the fluid arrives back in the fluid reservoir 28 from the drive unit 5 via a seventh fluid line 32g.

[0107] The exemplary fluid diagram for lubricating or supporting and cooling, respectively, the bearing points 13, 14, 15 and cooling the drive unit 5 shows a fluid circuit. This supply and return of the fluid is not illustrated in FIGS. 1 to 7.

[0108] This diagram of a fluid circuit for lubricating or supporting and cooling, respectively, the bearing points 13, 14, 15 and cooling the drive unit 5 merely represents a possible arrangement. It is for example also conceivable to configure the lubricating or supporting process and cooling process, respectively, of the bearing points 13, 14, 15 completely independently of the cooling process of the drive unit 5; the individual bearing points 13, 14, 15 could also be supplied with the fluid independently of one another. It is likewise conceivable that different fluids for cooling the drive unit 5 and the bearing points 13, 14, 15 are used, for example.

[0109] It goes without saying that the invention described here is not restricted to the embodiments mentioned and a plurality of modifications is possible. Therefore, instead of a grinding tool flange 3, the spindle shaft 2 can also have, for example, a mounting device for attaching a workpiece to be ground. The spindle shaft 2 would then not be a tool spindle but a workpiece spindle. These statements also apply analogously to a truing spindle. The drive unit does not necessarily have to be an electric motor with a stator unit surrounding the spindle shaft 2 and a rotor unit attached to the spindle shaft 2. Instead, other desirable drives from the prior art are conceivable, for example a belt drive or the like. The first bearing point 13 and/or the second bearing point 14 do not necessarily have to be conically formed, but could be formed from a hydrostatic radial bearing and a hydrostatic axial bearing in each case. A plurality of further modifications is conceivable.

LIST OF REFERENCE SIGNS

[0110] 1 Housing [0111] 2 Spindle shaft [0112] 3 Grinding tool flange [0113] 4 Grinding tool [0114] 5 Drive unit [0115] 6 Stator unit [0116] 7 Rotor unit [0117] 8 First end of the rotor unit [0118] 9 Second end of the rotor unit [0119] 10 Holding sleeve [0120] 11 First conical region [0121] 12 Second conical region [0122] 13 First bearing point [0123] 13a,b,c,d Bearing pocket [0124] 14 Second bearing point [0125] 14a,b,c,d Bearing pocket [0126] 15 Third bearing point [0127] 15a,b,c,d Bearing pocket [0128] 16 First pressure controller [0129] 17 Second pressure controller [0130] 18 Third pressure controller [0131] 19a,b,c Angle measuring device [0132] 20 First spindle end [0133] 21 Second spindle end [0134] 22 Insert sleeve [0135] 23a First sleeve support [0136] 23b Second sleeve support [0137] 24 Third sleeve support [0138] 25 Cooling channel [0139] 26 First fixed sleeve [0140] 27 Second fixed sleeve [0141] 28 Fluid reservoir [0142] 29 Drive motor [0143] 30 First fluid pump [0144] 31 Second fluid pump [0145] 32a-g Fluid lines [0146] 33 Pre-tension valve [0147] 34 Heat exchanger [0148] A Mounting portion [0149] B First bearing portion [0150] C Force-transfer portion [0151] D Second bearing portion [0152] RA Axis of rotation [0153] AR Axial direction [0154] RR Radial direction [0155] BL Bending line [0156] Opening angle