Drive for a grinding spindle   

The invention relates to a grinding spindle unit as specified in the preamble of claim 1.

DE 693 06 528 [U.S. Pat. No. 5,462,470] discloses a grinding-spindle assembly where the grinding wheel is mounted on a fixed shaft in a split housing. A rotor along with a flange supports a grinding stone at its outer periphery. The rotor is mounted on a fixed shaft in a radial magnetic bearing. A second magnetic bearing is provided to take up the axial forces. The drive motor is located either between the flange and the housing wall, or it is mounted laterally next to the grinding wheel between the inner periphery of the rotor and the outer periphery of the fixed shaft.

The object of the invention is to provide a grinding-spindle assembly with a compact drive.

This object is attained by a grinding-spindle assembly having the features of claim 1.

An advantageous aspect of the invention consists in the fact that the drive is implemented as a ring motor. Ring motors of the type used here are synchronous motors with an electric coil in the stator and multiple permanent magnets in the rotor. According to the invention, the rotor is a hollow shaft that accommodates the permanent magnets and supports the grinding-wheel tool. The fact that the grinding tool is mounted directly on the rotor produces a particularly space-saving construction. The stator with the coils is mounted on a fixed shaft that in an advantageous design accommodates the feed lines for electrical power and coolant. The fact that the mount holds the fixed shaft at both ends in the bearing blocks results in a very rigid design. However, the stator can also be mounted at only one end. In an advantageous embodiment, the grinding tool can be slid along its rotation axis, for example, to effect shift movements. To this end, the bearing blocks are movably guided on a bed along guides. With a two-ended mounting of the stator, it is possible to slide the bearing blocks apart along the guides for maintenance purposes. This facilitates installation and removal of the grinding tool.

The compact construction and provision of the ring motor inside a hollow shaft provides an especially rigid mounting for the grinding tool. This tool can then be advantageously employed to machine gear teeth based on the gear-generation or partial-gear-generation method.

The following discussion explains the invention in more detail based on an illustrated embodiment. Therein:

FIG. 1 is a front partly sectional view of the grinding unit;

FIG. 2 shows the grinding unit of FIG. 1 with a shift axle;

FIG. 3 is a side partly sectional view of the grinding unit.

In the grinding unit of FIG. 1, the shaft 2 is rotationally fixed in mounting blocks 3 and 3′. The stator 4 with coils 5 is fixed on the shaft 2. The shaft 2 has supply passages 6 and 6′ and a helicoidal passage 7 through which coolant to cool the ring motor is supplied and removed. The power-supply passages for the coils 5 are routed through the passage 8. Bearings 9 and 9′ for a rotor 10 are mounted in the shaft 2 axially flanking the stator 4. Permanent magnets 11 are located level with the stator 4 on the inside wall of rotor 10. The grinding tool 14 is clamped on the outer periphery of the rotor 10 between flange rings 12 and 12′. The flange rings 12 and 12′ are in turn clamped radially to the rotor 10 by expansion chucks 13. A hob-grinding wheel serving as a grinding tool 14 serves for machining gear teeth. The rotor 10, formed as a hollow shaft, the internally mounted stator 4, and the externally attached grinding tool 14 provide an especially compact and torsionally rigid construction.

FIG. 2 shows the grinding unit of FIG. 1 with a shift axle. A bed 16 is pivotal about an axis 19 in an unillustrated grinding machine.

Pivoting about the axis 19 is required, for example, in order to be able to machine helical gear teeth. A pivot motor 20 functions as the drive here. The bed 16 carries guides 15 mounted on the bed 16 on which bearing blocks 3 and 3′ with slide shoes 17 and 17′ are guided in a linearly movable fashion. The grinding tool 14 can be moved along the guides 15 in the direction of its rotation axis 23. The motor 18 can be provided as the drive for these motions, the motor moving the bearing blocks 3 and 3′ by means of an unillustrated threaded spindle. The bearing blocks 3 and 3′ can be moved apart as required. As a result, installation and removal of grinding tool 14 is facilitated.

FIG. 3 shows a cross-section through the grinding unit of FIG. 2. For purposes of pivoting about the axis 19, the bed 2 is mounted in a pivot bearing 21. The pivot motor 20 is effectively connected to the bed 2 through a worm drive 24. After pivoting, the bed 2 is fixed in place by clutches 22.

1 grinding unit

2 shaft

3 3′ bearing block

4 stator

5 coil

6 6′ supply passage

7 cavity

8 passage

9 9′ bearing

10 rotor

11 permanent magnet

12 12′ flange ring

13 expansion chuck

14 grinding tool

15 guide

16 bed

17 17′ slide shoe

18 motor

19 pivot axis

20 pivot motor

21 pivot bearing

22 clutch

23 rotation axis

24 worm drive