MACHINE TOOL UNIT WITH A TOOL CLAMPING DEVICE

Abstract

A motor-driven machine-tool unit such as a multi-axis turning head or a motor spindle, having a stator unit and at least one rotor unit that is rotatable about a rotation axis, wherein the rotor unit comprises at least one tool receptacle unit having a tool clamping device that is adjustable in a longitudinal direction of the rotation axis and impingeable with a clamping force, for fixing and bracing a releasably fixable tool, wherein comparatively high requirements are met, in particular, in terms of the accuracy of the machining and/or the reliability in the machining. According to the present invention, this is achieved above all in that at least two clamping force sensors are provided for detecting the bracing of the tool clamping device, in particular the clamping force that is caused in the fixing and bracing.

Claims

1. A motor-driven machine-tool unit comprising a stator unit, a rotor unit that is rotatable about at least one rotation axis, wherein the rotor unit comprises at least one tool receptacle unit having a tool clamping device that is adjustable in a longitudinal direction of the rotation axis and impingeable with a clamping force for fixing and bracing a releasably fixable tool, and at least two clamping force sensors for detecting the bracing of the tool clamping device, wherein, in order for the position and/or the alignment of the rotation axis to be determined in a machining procedure of the machine tool the at least two clamping force sensors are: (i) configured as proximity sensors for detecting a spacing between the rotor unit and the stator unit, (ii) configured as deformation sensors for detecting a deformation of at least part of the rotor unit and/or of the tool receptacle unit that is generated by the clamping force, and (iii) disposed at mutually dissimilar angular positions about the rotation axis and/or are disposed symmetrically about the rotation axis.

2. The machine-tool unit as claimed in claim 1, wherein the at least two clamping force sensors are configured as radial sensors having in each case at least one detection region which is aligned so as to be perpendicular to the longitudinal direction of the rotation axis.

3. The machine-tool unit as claimed in claim 1, wherein at least two neighboring clamping force sensors of the at least two clamping force sensors have a mutual angular position of 90.

4. The machine-tool unit as claimed in claim 2, wherein the rotation axis is disposed in the at least two detection regions of the at least two clamping force sensors.

5. The machine-tool unit as claimed in claim 1, wherein at least one of the clamping force sensors is provided as an axial sensor having at least one detection region that is aligned in the longitudinal direction of the rotation axis, said at least one of the clamping force sensors being configured as a proximity sensor for detecting a spacing in the axial direction between the rotor unit and the stator unit.

6. The machine-tool unit as claimed in claim 1, wherein the rotor unit has a protrusion that is aligned in the radial direction, and/or an arm that is aligned in the radial direction, and the axial sensor is aligned such that the protrusion and/or the arm is in the detection region of the axial sensor, so as to detect a displacement of the rotor unit in the axial direction, and/or to measure any tilting of the rotation axis.

7. The machine-tool unit as claimed in claim 1, wherein the clamping force sensor is disposed in the direction of the rotation axis in the region of the tool clamping device and/or of the tool receptacle unit.

8. The machine-tool unit as claimed in claim 1, wherein the clamping force sensor is disposed on and/or in the stator unit.

9. The machine-tool unit as claimed in claim 1, wherein the clamping force sensor is disposed on and/or in the rotor unit and comprises a transmission unit for transmitting measured data.

10. The machine-tool unit as claimed in claim 1, wherein the clamping force sensor is configured as an inductive and/or optical and/or magnetic sensor, and/or as an ultrasonic sensor.

11. A machine tool having a machine-tool unit as claimed in claim 1.

12. A method for clamping a releasably fixable tool in a machine-tool unit, wherein a rotor unit that is rotatable about a rotation axis uses at least one tool receptacle unit having a tool clamping device that is adjustable in a longitudinal direction of the rotation axis and impingeable with a clamping force for fixing and bracing a releasably fixable tool, wherein at least during and/or after the adjustment and the bracing of the tool clamping device that is directed in the longitudinal direction of the rotation axis, for fixing the tool and/or in the case of a fixed tool, at least two clamping force sensors detect the bracing of the tool clamping device, wherein clamping force sensors which are configured as follows are used as such clamping force sensors: the at least two clamping force sensors are configured as proximity sensors for detecting a spacing between the rotor unit and the stator unit; the at least two clamping force sensors are configured as deformation sensors for detecting a deformation of at least part of the rotor unit and/or of the tool receptacle unit that is generated by the clamping force; the at least two clamping force sensors are disposed at mutually dissimilar angular positions about the rotation axis and/or are disposed symmetrically about the rotation axis; wherein the at least two clamping force sensors measure the clamping force by way of a deformation of at least part of the rotor unit that runs symmetrically about the rotation axis and is caused by the action of the clamping force, and determine the position and/or alignment of the rotation axis in a machining procedure of the machine tool.

13. The method as claimed in claim 12, wherein the at least two clamping force sensors are configured as radial sensors having in each case at least one detection region which is aligned so as to be perpendicular to the longitudinal direction of the rotation axis; at least a third clamping force sensor is used as an axial sensor having at least one detection region that is aligned in the longitudinal direction of the rotation axis; said axial sensor being configured as a proximity sensor for detecting a spacing in the axial direction between the rotor unit and the stator unit; a rotor unit which has a protrusion that is aligned in the radial direction and/or has an arm that is aligned in the radial direction is used as such a rotor unit; wherein the axial sensor by way of the detection region thereof detects the protrusion and/or the arm; and measures a displacement of the rotor unit in the axial direction and/or by a tilting of the rotation axis.

14. The machine-tool unit as claimed in claim 1, wherein the unit is a multi-axis turning head or a motor spindle.

15. The machine-tool unit as claimed in claim 1, wherein the clamping force sensors detect the clamping force that is caused in the fixing and bracing.

16. The machine-tool unit as claimed in claim 1, wherein the clamping force sensors measure the clamping force across a deformation of at least part of the rotor unit that runs symmetrically about the rotation axis and is caused by the action of the clamping force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] An exemplary embodiment of the present invention is illustrated in the drawing and will be explained in more detail hereunder by means of the figures.

[0052] FIG. 1 shows a schematic sectional fragment of a motor spindle according to the present invention with a radial sensor;

[0053] FIG. 2 shows a schematic sectional fragment of a motor spindle according to the present invention with an axial sensor; and

[0054] FIG. 3 shows a schematic cross section in the direction of the rotation axis of the motor spindle according to FIG. 2, with two axial sensors according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0055] A collet chuck 1 having a plurality of clamping segments 2 is illustrated schematically in a section in a motor spindle 3 of a machine tool in each of FIGS. 1 and 2. As is customary in machine tool engineering, one side of the collet chuck 1 is illustrated in the non-tensioned state (part almost not illustrated) and in the tensioned state of the motor spindle 3 or of the collet chuck 1, respectively.

[0056] A clamping force sensor 4 according to the present invention can be seen in the tensioned part of the motor spindle 3 illustrated in the figures. This sensor 4 in FIG. 1 has an effective region that is aligned in a radial manner, and in FIG. 2 has an effective region that is aligned to the rotation axis D. Accordingly, a radial sensor 4 in the context of the present invention is illustrated in FIG. 1, and an axial sensor 4 in the context of the present invention is illustrated in FIG. 2. However, a second corresponding sensor 4 according to the present invention cannot be seen in each case in either of FIGS. 1 and 2, since the second sensor 4 is in each case disposed so as to be offset, in particular by 90, in the circumferential direction and is thus invisible in the sectional illustrations. The arrangement of the two sensors 4 according to the present invention can be seen in FIG. 3.

[0057] A region X, illustrated schematically in FIG. 1, of a spindle shaft 5, or of a counter holder 6, respectively or of a detent/ring element 6, respectively, of the motor spindle 3 is deformed or widened, respectively, in the radial direction R on account of the bracing of the tool (not illustrated in more detail), or on account of a readjustment of the collet chuck 1 or of the clamping segments 2, respectively, that is directed axially in the direction of the rotation axis D. An element 7 of the spindle shaft 5 herein transmits a clamping force F, or a deformation/modification of a tool receptacle unit 8 to the element 6. A spacing 9, or an air gap 9, respectively, between the rotor unit or the spindle shaft 5, respectively, and a stator unit 10 having the radial sensor 4 is modified or reduced in size, respectively, on account thereof. The modification of the deformation in the region X on account of the bracing is the nominal deformation in the context of the present invention, and a modification of the detected actual deformation is accordingly used in an advantageous manner for regulating/controlling the motor spindle 3.

[0058] An axially aligned deformation of a measuring arm 11, or an axial modification A of the spacing 9, respectively in FIG. 2 is detectable and further processable by way of the axial sensor 4. This axial modification A is in turn generated by a clamping force F or by a radial deformation/modification of the tool receptacle unit 8, respectively, acting on the element 6.

[0059] A cross section through the variant according to FIG. 2 is illustrated in a highly schematic manner in FIG. 3, wherein the advantageous arrangement of the two sensors 4 according to the present invention is highlighted. These two sensors 4, like two radially oriented sensors 4 (also not illustrated in more detail) according to FIG. 1 are disposed so as to be offset by preferably 90 in the circumferential direction. The exact position/alignment of the rotation axis D can be detected or determined, respectively, in an advantageous manner herewith. Symmetrical or non-symmetrical deformations/modifications of the counter holder 6, or of the detent/ring element 6, respectively, of the motor spindle 3 and/or of the tool receptacle unit 8 can be detected and be appraised/evaluated in an advantageous manner by the two sensors 4.