Machine tool unit having tool sensor for detecting load of tool

Abstract

The invention relates to a machine tool unit driven by an electric motor, comprising a stator unit (2) and a rotor unit (3), which has at least one rotor shaft (105) and can be rotated about an axis of rotation (D), said rotor unit (3) comprising at least one tool receiving unit, the tool receiving unit has a tool clamping device for fixing and clamping a releasably fixed shank of the tool (50), at least one tool sensor (5) is provided for detecting a load on the tool (50), and at least one electromagnetic drive system is provided for driving the tool (50) on the tool receiving unit. The machine tool unit has improved accuracy and / or by means of the machine tool unit, the accuracy of machining by a corresponding machine tool can be improved. This is achieved according to the invention in that at least one weakening structure (30) is arranged between the tool sensor (5) and the axis of rotation (D) in order to increase the mechanical offset when the tool (50) is loaded and / or when the loading situation of the rotor unit (3) or a component thereof changes.

Description

Technical Field

[0001] The invention relates to a motor-driven machine tool unit, such as a multi-axis rotary head or a motor spindle, according to the preamble of claim 1 . Background Art

[0002] In machine tools there are various exchangeable devices or tools which are connected to the machine tool via standardized standard interfaces.

[0003] These are primarily tools which are connected to a machine spindle or motor shaft via a releasable conical connection and in which a so-called clamping head is opened or closed by an axial movement so that the axial forces required for securely fixing the tool can be transmitted to the tool or can also be released again afterwards.

[0004] EP 1 889 685 B1 already discloses a machine tool in which the surface contour of the circumference of the spindle head is checked for deformation using a pointer gauge. This deformation is then attributed to the presence of foreign matter, such as chips, in the area between the outer surface of the tool and the inner surface of the tool holder.

[0005] However, as machine tools are required to have higher precision and reliability, this is no longer enough. Summary of the invention

[0006] The object of the present invention is to specify a motor-driven machine tool unit which has increased precision and / or by means of which the precision of machining by a corresponding machine tool can be increased.

[0007] Starting from a machine tool unit of the aforementioned type, this object is achieved by the features of claim 1. Advantageous embodiments and developments of the invention are made possible by the measures specified in the dependent claims.

[0008] Accordingly, the machine tool unit according to the invention is characterized in that at least one weakening structure is provided between the tool sensor and the axis of rotation in order to increase and / or reduce the mechanical deflection when the tool is loaded and / or when the load conditions of the rotor unit or its parts change.

[0009] The weakening structure described here achieves an increase in the sensitivity of the sensor mechanism and thus achieves better results or higher precision. This has a positive effect on the precision of the machine tool. The sensor mechanism is understood here to mean the sensor and the sensor element to be detected or detected by means of it. By an advantageously greater deformation of the sensor element or a change in the sensor surface to be detected and / or the distance of the sensor element to be detected from the “actual” sensor, the sensor mechanism is significantly improved, even though the “actual” sensor is (usually) not changed / improved.

[0010] Advantageously, the weakening structure is designed as a cantilever of the tool sensor and / or as a cantilever of the sensor element of the tool sensor. In this case, the sensor element of the tool sensor is weakened in an advantageous manner, so that under corresponding loads or under changing load conditions, deflections or deformations of the sensor element or the cantilever are suppressed to a lesser extent and increased accordingly. This advantageously increases the sensitivity of the sensor arrangement.

[0011] In an advantageous variant of the invention, the weakening structure is designed as a recess in the rotor unit and / or the rotor shaft and / or as a recess in the tool receiving unit. The recess weakens the stability of the corresponding component, thereby enabling a greater deformation or a higher precision of the sensor device.

[0012] Advantageously, the recess is formed on a radially outwardly oriented surface of the rotor unit and / or the rotor shaft and / or the tool receiving unit, and / or the recess is formed on a radially inwardly oriented surface of the rotor unit and / or the rotor shaft and / or the tool receiving unit. In this way, the recess can be advantageously produced, thereby reducing the manufacturing expenditure and / or cost expenditure.

[0013] For example, the weakening structure and / or the recess is arranged between the tool sensor and the tool receiving unit, viewed in the radial direction, and / or between the tool sensor and the axis of rotation, viewed in the radial direction. Preliminary tests have shown that such a weakening has a very positive effect on the measurable deformation or higher precision of the sensor mechanism in these areas.

[0014] Advantageously, the weakening structure and / or the recess is arranged between the tool sensor and the first rolling bearing, viewed in the axial direction, and / or the weakening structure and / or the recess is arranged between the tool receiving unit and the first rolling bearing, viewed in the axial direction. Here, too, such weakening has a positive effect on the achievable accuracy.

[0015] In a particular improvement of the invention, the recess is configured as a cavity inside the rotor unit and is in particular completely surrounded by the material and / or components of the rotor unit. The weakening structure and / or the recess at least comprises air, for example. This makes it possible to advantageously implement the recess, thereby reducing manufacturing costs and / or cost costs.

[0016] Advantageously, the weakening structure comprises at least plastic. Alternatively or in combination therewith, it comprises at least metal. In particular, the weakening structure is not made of steel, but for example of copper, aluminum or a corresponding alloy or the like. This can also advantageously increase the sensitivity and can also be manufactured cost-effectively.

[0017] Usually, the rotor unit that rotates relative to the stator unit belongs to the motor shaft drive. The actual cutting tool (milling cutter, drill bit, etc.) is usually held or clamped in a tool holder, which is arranged in a tool clamping device, which is considered to be part of the spindle head of the rotor unit. For this purpose, the tool clamping device has a holding device for the tool holder. The tool clamping device is usually subjected to a clamping force and is adjusted in the longitudinal direction of the axis of rotation. A part of the clamping device can be pulled into a retracted receiving part, for example, so that the tool holder or the tool can be clamped again by means of radially acting forces. By releasing the clamping force, the clamped tool can usually be released again and the tool can be removed from the machine tool or replaced.

[0018] The actual sensor is mainly accommodated in the so-called sensor head; the sensor measures its distance from the rotor unit and / or the sensor element, wherein the sensor or a large part of the sensor is usually arranged in the stator unit. The sensor data is advantageously processed or evaluated by an electronic unit or evaluation electronics, which can be controlled by a computer.

[0019] The at least one sensor head is usually arranged at a fixed position on the stator unit in the region of the tool clamping device and can measure / detect so-called sensor elements at the end and / or laterally of the rotating spindle head of the rotor unit.

[0020] However, the sensor or sensor head can also be arranged in a variable position. Often, for example, chips clamped between the tool and the tool clamping device / spindle / rotor unit cause the tool to no longer run exactly centered / straight around the axis of rotation or the tool clamping device is slightly (also elastically) deformed and can no longer ensure constant concentricity or axial runout of the tool or tool holder, nor can it ensure rotation without angular changes. In general, concentricity defects often lead to specific damage during the machining process. Such displacements and / or deformations usually occur laterally and in the end / axial direction and can in principle also be detected there. At the end face, the distance is measured parallel to the axis of rotation, and the radial distance relative to the axis of rotation is measured laterally. All these displacements and / or deformations and the displacement of the rotor unit can be determined in this way and method. The precision or sensitivity can be increased here by weakening the structure.

[0021] The measurement can in principle be carried out at an angle of 90° to the surface of the rotor unit and / or the axis of rotation, but can also be carried out at angles deviating therefrom.

[0022] Especially in machine tools, high demands are placed on machining accuracy. The tool and therefore the cutting edge must usually be inserted into a tool holder or tool clamping device and moved in a precisely defined manner during machining, so that the workpiece to be machined is machined within predefined tolerance limits. Even if the machine tool and in particular the tool clamping device are manufactured with the required accuracy, other factors may arise during the use of the machine which often prevent the specified concentricity / axial runout from being maintained or the absence of angular errors. For example, during operation of the machine, chips generated during machining may stick to or jam on the tool and prevent the tool from rotating in the actual target position. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Exemplary embodiments of the invention are illustrated in the drawings and are explained in greater detail below with reference to the drawings.

[0024] Specifically, it shows:

[0025] Figure 1 A schematic diagram showing a first machine tool unit according to the present invention,

[0026] Figure 2 A schematic diagram showing three different spindle embodiments according to the prior art,

[0027] Figure 3 shows a schematic, cut-away detail of a motor shaft with a radial sensor according to the prior art,

[0028] Figure 4 shows a schematic, cut-away detail of a further motor shaft with an axial sensor according to the prior art,

[0029] Figure 5 A schematic diagram showing a first sensor unit having a first recess according to the present invention,

[0030] Figure 6 A schematic diagram showing a second sensor unit having a second recess according to the present invention,

[0031] Figure 7 A schematic diagram showing a third sensor unit having a third recess according to the present invention, and

[0032] Figure 8 A schematic diagram of a fourth sensor unit having a first cantilever according to the present invention is shown. DETAILED DESCRIPTION

[0033] Figure 1 A schematic diagram of a section of a machine tool unit 1 with a part of a stator unit 2 and a part of a rotor unit 3 is shown, wherein Figure 1In the figure, the main spindle head as part of the rotor unit 3 can be seen. The stator unit 2 has, for example, a ring 4, on which a sensor head or sensor 5, for example in the form of an axial sensor, is arranged. The rotor unit 3 comprises, for example, a measuring ring or sensor element 6 made of metal, which is advantageously made of a paramagnetic material. The axial sensor or sensor 5 is arranged so that it measures the distance from the end side of the rotor unit 3. However, lateral measurements in the radial direction relative to the rotation axis D are also conceivable. This surface for determining the distance is located on the measuring ring or sensor element 6. The axial sensor or sensor 5 is designed, for example, as an eddy current sensor, so that as precise a measurement as possible can be achieved despite possible contamination.

[0034] The sensor head / axial sensor or sensor 5 is connected, for example, to an electronics unit 7 ; together they form a testing device 8 which in turn is connected to a machine control 9 so that control interventions can be carried out as required in the event of excessive axial runout.

[0035] In a special development, for example, only one sensor head or sensor 5 is provided. It is conceivable to additionally use a trigger sensor, for example for detecting an optical reference mark on the measuring ring or sensor element 6, wherein the trigger sensor can also be arranged on the sensor ring 4, for example. The mark can also be designed as a groove or the like. With the aid of such a trigger sensor, only the starting point for the measurement is triggered, whereby the phase relationship of the measured values ​​to one another can be determined more easily during the evaluation. The trigger sensor is not absolutely necessary and is not required in the case of a trigger sensor. Figure 1 Not further shown.

[0036] The stator unit 2 comprises, for example, a cover 10 for the sensor ring 4 and also a bearing cover 11. The tool clamping device 12 (in Figure 1 The rotor unit 3 is shown as a conical ring.

[0037] exist Figure 2 Schematically shows three different variants of a spindle according to the prior art, wherein an electromagnetic drive system 120 is arranged between a so-called front spindle bearing 121 and a so-called rear spindle bearing 122 (see Figure 2 a)) or arranged behind the so-called rear spindle bearing 122 (see Figure 2 b)) or by means of a coupling unit 126 which is again arranged at the so-called rear spindle bearing 122 (see Figure 2 c)). The main shaft bearings 121 , 122 are provided for supporting the rotatable rotor unit 3 or the rotor shaft 105 or the main shaft 105 .

[0038] exist Figure 3 and 4, two further variants according to the prior art are shown, wherein a motor shaft 3 of a machine tool is shown in section. As is customary in machine tool construction, the side of the clamping head 1 with the plurality of clamping sections 2 is in the unclamped state (part barely shown) and in the clamped state of the motor shaft 3 or the clamping head 101 or the spindle head 1.

[0039] exist Figure 3 and 4 The sensor 104 can be seen in the clamped portion of the motor shaft 3 shown. Figure 3 has a radially oriented active area and Figure 4 has an active area oriented along the axis of rotation D. Thus, in Figure 3 The radial sensor 104 is shown in Figure 4 The axial sensor 104 is shown in FIG. Figure 3 and 4 The second sensor or the third sensor which may optionally be used cannot be seen in the sectional view, since they are each arranged offset in the circumferential direction, in particular by 90° or 180°, etc., within the scope of use and are therefore not visible in the sectional view.

[0040] Changes in the spindle head 1 or the application of loads or forces directed axially and / or radially relative to the axis of rotation D by a tool or clamping head 101 (not specifically shown) cause the spindle 105 or the motor shaft 103 to be axially and / or radially oriented relative to the axis of rotation D. Figure 3 The region X schematically shown in FIG. 1 is deformed or widened in the radial direction R. In this case, the element 107 of the spindle 105 transmits the clamping force F or the displacement and / or deformation, i.e. the change, to the element 106. As a result, the distance A or the air gap 109 between the rotor unit or the spindle 105 and the stator unit 100 with the radial sensor 104 is changed or reduced. The state in the region X according to the aforementioned reference measurement is the target state, and the detected actual displacement and / or deformation due to the force / change in the region of the spindle head 1 The change or actual state is used in an advantageous manner to monitor / control the motor shaft or the rotor unit 3.

[0041] exist Figure 4 In the embodiment of the present invention, an axially oriented deformation of the measuring arm 111 and the axial sensor 104 or an axial change A of the distance 109 can be detected and further processed. The axial change A is in turn produced by a force / change F at the tool 50 or at / in the spindle head 1 or an axial and / or radial deformation / change at the tool 50 or the spindle head 1, which is transmitted to the tool receiving unit 108 and the element 106 and thus ultimately to the measuring arm 111 or its detectable sensor surface / distance 109.

[0042] exist Figures 5 to 8 1 and 2 show different variants according to the invention (partially cut away). Various weakening structures 30, 31 are present here. The sensor element 6 or the sensor surface of the sensor element 6 which is spaced apart from the sensor 5 and detectable is arranged on the measuring ring 106 or is optionally designed integrally with the measuring ring 106 which can rotate about the rotation axis D. The measuring ring 106 is fixed by means of a threaded ring 125, in particular pressed onto the front bearing 121 or its inner ring.

[0043] In accordance with Figure 5 In a variant of , a recess 30 is provided which is designed as a groove in the rotor shaft 105 or the main shaft 105 and is covered by the measuring ring 106 .

[0044] In accordance with Figure 6 In a variant of , a recess 30 is provided which is designed as a groove of the measuring ring 106 and is realized as an open groove.

[0045] In accordance with Figure 7 In a variant of , a recess 30 is provided which is designed as a groove of the measuring ring 106 and is covered by the rotor shaft 105 or the main shaft 105 .

[0046] In accordance with Figure 8 In a variant of , a recess of the measuring ring 106 is provided as a cantilever 31 , on which the sensor element 6 or the sensor surface of the sensor element 6 which is spaced apart from the sensor 5 and can be detected is arranged.

Claims

1. A motor-driven machine tool unit, such as a multi-axis rotary head or a motor shaft, comprising a stator unit (2) and a rotor unit (3) having at least one rotor shaft (105) and rotatable about an axis of rotation (D), wherein: The rotor unit (3) comprises at least one tool receiving unit (101), which has a tool clamping device (102) which is adjustable, in particular in the longitudinal direction of the rotation axis (D) and can exert a clamping force, and is used to fix and clamp a releasably fixed tool holder of a tool (50), wherein at least one tool sensor (5) is provided for detecting the load of the tool (50), wherein a distance (109) is provided between the tool sensor (5) and the rotation axis (D), wherein at least one first main bearing (121), in particular a front rolling bearing, and a second main bearing are provided between the rotor unit (3) and the stator unit (2). A bearing (122), in particular a rear rolling bearing, wherein, viewed in the axial direction, the tool sensor (5) is arranged between the first main bearing (121) and the tool clamping device (101) and / or the tool holder, wherein at least one electromagnetic drive system (120) is provided and, in particular, is arranged, viewed in the axial direction, between the first main bearing (121) and the second main bearing (122), characterized in that at least one weakening structure (30, 31) is provided between the tool sensor and the axis of rotation in order to increase the mechanical offset when the tool (50) is loaded and / or when the load conditions of the rotor unit (3) or its components change.

2. The machine tool unit according to claim 1, characterized in that: The weakening structure (30, 31) is designed as a cantilever (31) of the tool sensor (5) and / or of a sensor element (6) of the tool sensor (5).

3. A machine tool unit according to any one of the preceding claims, characterized in that The weakening structure (30, 31) is designed as a recess (30) of the rotor unit (3) and / or of the rotor shaft (105).

4. A machine tool unit according to any one of the preceding claims, characterized in that The weakening structure (30, 31) is designed as a recess (30) of the tool receiving unit (101).

5. A machine tool unit according to any one of the preceding claims, characterized in that The recess (30) is formed on a surface of the rotor unit (3) and / or the rotor shaft (105) and / or the tool receiving unit (101) which is oriented radially outward.

6. A machine tool unit according to any one of the preceding claims, characterized in that The recess (30) is formed on a surface of the rotor unit (3) and / or the rotor shaft (105) and / or the tool receiving unit (101) which is oriented radially inwards.

7. A machine tool unit according to any one of the preceding claims, characterized in that Viewed in the radial direction, the weakening structure (30, 31) and / or the recess (30) is arranged between the tool sensor (5) and the tool receiving unit (101).

8. A machine tool unit according to any one of the preceding claims, characterized in that Viewed in the radial direction, the weakening structure (30, 31) and / or the recess (30) is arranged between the tool sensor (5) and the axis of rotation (D).

9. A machine tool unit according to any one of the preceding claims, characterized in that Viewed in the axial direction, the weakening structure (30, 31) and / or the recess (30) is arranged between the tool sensor (5) and the first rolling bearing (121).

10. A machine tool unit according to any one of the preceding claims, characterised in that Viewed in the axial direction, the weakening structure (30, 31) and / or the recess (30) is arranged between the tool receiving unit (101) and the first rolling bearing (121).

11. A machine tool unit according to any one of the preceding claims, characterized in that The recess (30) is designed as a cavity (30) within the rotor unit (3) and is in particular completely surrounded by material and / or components of the rotor unit (3).

12. A machine tool unit according to any one of the preceding claims, characterized in that The weakened structure (30, 31) and / or the recess (30) at least contains air.

13. A machine tool unit according to any one of the preceding claims, characterised in that The weakening structure (30, 31) comprises at least plastic.

14. A machine tool unit according to any one of the preceding claims, characterised in that The weakening structure (30, 31) comprises at least metal and / or does not consist of steel.

15. A machine tool having a tool (50) and a machine tool unit according to any of the preceding claims.

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