METHOD AND DEVICE FOR BALANCING

Abstract

Methods of balancing a workpiece, in which the workpiece is rotated about an axis of rotation. The forces and/or torques that result from an unbalance of the workpiece during the rotation of the workpiece are measured, and material is removed from the workpiece to reduce the unbalance. The method includes removal of material from the rotating workpiece during measuring or as the workpiece is continuously rotated between measuring and material removal.

Claims

1.-16. (canceled)

17. A method for balancing a workpiece, comprising rotating the workpiece about an axis of rotation; measuring the forces and/or torques and/or oscillations that result during the rotation of the workpiece from an unbalance of the workpiece; and removing material of the workpiece so as to reduce the unbalance, wherein the material is removed from the rotating workpiece during said measuring or the workpiece is continuously rotated between said measuring and said removing of material.

18. The method of claim 17 wherein the material of the workpiece is removed by a defined or undefined cutting edge to reduce the unbalance.

19. The method of claim 17 wherein the material of the workpiece is removed in a direction radially and/or parallel and/or obliquely to the axis of rotation to reduce the unbalance.

20. The method of claim 17 wherein during said removing of material, advancement occurs by way of a relative movement between the workpiece and a machining means.

21. The method of claim 20 wherein said relative movement takes place by way of a movement of the workpiece and/or by way of a movement of the machining means.

22. The method of claim 20 wherein during said removing of material of the workpiece to reduce the unbalance, advancement occurs cyclically.

23. The method of claim 17 wherein the workpiece comprises at least one balancing body, wherein the material of said balancing body is removed to reduce the unbalance, wherein a non-round outer contour of the balancing body is created.

24. The method of claim 23 wherein the workpiece comprises a plurality of separate balancing bodies, the material thereof being removed at the same time to reduce the unbalance.

25. A device for balancing a workpiece, comprising: a clamping unit configured to clamp the workpiece; a rotary drive configured to rotate the workpiece about an axis of rotation; a one sensor configured to measure forces and/or torques and/or oscillations caused by an unbalance of the workpiece during rotation; and at least one machining unit configured to remove material from the workpiece responsive to signals of the sensor such that material is removed during rotation of the workpiece so as to reduce the unbalance.

26. The device of claim 25 wherein the machining unit comprises a machining means which interacts with the workpiece to remove the material.

27. The device of claim 26 wherein the machining means comprises a grinding unit with a grinding disk or a grinding belt.

28. The device of claim 26 wherein the machining means is of stationary or movable design.

29. The device of claim 25 wherein the machining unit is configured to move parallel to the axis of rotation.

30. The device of claim 25 comprising a plurality of machining units arranged spaced apart along the axis of rotation.

31. The device of claim 25 wherein the clamping unit comprises bearing means configured to receive shaft seats of the workpiece or a centering spindle for end-side fastening of the workpiece.

Description

[0040] In the figures:

[0041] FIG. 1 shows a frontal view of a device for balancing a workpiece according to an exemplary embodiment according to the invention, with a grinding unit, that can be moved parallel to the axis, with a grinding disk;

[0042] FIG. 2 shows a detailed view of the grinding unit according to FIG. 1 from the side;

[0043] FIG. 3 shows a frontal view of a device for balancing a workpiece according to a further exemplary embodiment according to the invention, with a grinding belt for machining the bearing seats;

[0044] FIG. 4 shows a detailed view of the grinding unit according to FIG. 3 from the side and

[0045] FIG. 5 shows a balancing body, machined according to the invention, which has been ground to a crown or in a nonround manner from a circular starting shape;

[0046] FIG. 6 shows an alternative embodiment of the exemplary embodiment according to FIGS. 1 and 2, in which the machining means can be advanced in a translatory manner;

[0047] FIG. 7 shows a rotor, in the case of which the balancing is performed at balancing disks;

[0048] FIG. 8 shows an asynchronous rotor, in the case of which the balancing is performed at short-circuiting rings;

[0049] FIG. 9 shows a rotor, in the case of which the balancing is performed at the circumferential surface of a laminated core.

[0050] FIG. 1 shows an example for a device for balancing a workpiece 10, in particular for balancing a rotor for an electric motor. In the context of the invention, the device per se, i.e. without the workpiece 10, is also disclosed and claimed. As illustrated in FIG. 1, the device is, however, also disclosed and claimed together with the workpiece 10 to be balanced.

[0051] The device comprises a clamping unit 30 with bearing means 31 to support the shaft seats 32 of the workpiece 10. Instead of the bearing means 31, a centering spindle 33, as shown in FIG. 3, can be used if it is intended for the bearing seats 32 to be machined. The clamping unit 30 defines an axis of rotation 11, about which the workpiece 10 can be rotated in the clamped-in state, as shown in FIG. 1. The rotational movement is created by a rotary drive 13, as shown by way of example in FIG. 2. The rotary drive 13 may be embodied as a roller drive. Other rotary drives 13 are possible.

[0052] The device comprises at least one sensor, in particular a plurality of sensors (not illustrated), which are designed to measure the forces and/or torques and/or oscillations that act or result on account of an unbalance of the workpiece 10 during rotation. The sensors are connected to a data processing unit, which is likewise not illustrated. The data processing unit is configured or adapted to process and forward the sensor signals for activation of the machining unit 20.

[0053] In the example according to FIG. 1, the machining unit 20 is designed as a grinding unit 22 with a grinding disk 23. As shown in FIG. 2, the grinding disk 23 can be moved, in the example of FIG. 2 is mounted in a tiltably movable manner (see double-headed arrow), so that an advancing movement in a radial direction perpendicular to the axis of rotation 11 is possible. The grinding disk 23 and the workpiece 10 rotate in opposite directions. Another possibility of bringing about the relative movement between the workpiece 10 and the grinding disk 23 is indicated in FIG. 6. Here, the grinding disk 23 is moved linearly in the direction of the workpiece 10, in order to control the mechanical removal of material.

[0054] The machining unit 20, specifically the grinding unit 22, can be activated on the basis of the signals of the sensor or of the sensors. The aforementioned data processing unit, which is connected to the sensor or to the sensors, may carry out the activation. The activation of the grinding unit 22, specifically the advancing movement, is effected on the basis of the signals of the sensor such that the material of the workpiece 10 is removed to reduce the unbalance. There is a direct relationship between the measurement operation and the material removing on account of the signal connection between the sensors and the grinding disk 21. In the example, the workpiece 10 is equipped with two balancing bodies 12 in the form of disks, specifically on the shaft of the workpiece 10. To reduce the unbalance, in the example material is removed from the balancing bodies 12 of the workpiece 10. Another number of balancing bodies 12 is possible. The grinding unit 22 can be moved parallel to the axis of rotation 11 so that the two balancing bodies 12 can be machined by one and the same grinding unit 22.

[0055] The balancing process is continued until a desired balance quality is achieved. For high-rotational-speed rotors, this can be e.g. a balance quality G of 2.5 or better (c.f. the international standard to ISO 1940-1).

[0056] A possible process sequence for the example is as follows: The workpiece 10 is clamped in and rotated at a first target rotational speed. Then, the balancing process begins. An unbalance is determined by suitable means and transferred to a control unit (not shown) (step 1). The workpiece is accelerated to a second target rotational speed appropriate for the grinding process and machined by means of the grinding unit in accordance with the control presets of the control unit (step 2). Subsequently, the workpiece is moved back to the first target rotational speed, and the unbalance is measured again (step 1). If the determined balance quality does not yet correspond to the desired balance quality, steps 2 and 1 are repeated until the desired balance quality is achieved.

[0057] If said balance quality is achieved, the balancing process is ended; the workpiece is then slowed down to a standstill and unclamped. Characteristic of this method example according to the invention is that, during the entire balancing process, the workpiece is not slowed down to a standstill but rotates continuously. The rotational speed may vary here, in particular between the measurement operation and the material removing operation. Nevertheless, during the actual method, the workpiece never achieves a speed of zero.

[0058] Furthermore, the machining device 20 may be configured such that a further surface machining of the outer circumference of the workpiece, e.g. of the surface of a laminated core, may also be effected in this way.

[0059] Where the workpiece 10 provides sufficiently non-functional dead material, which can be removed to reduce the unbalance, balancing disks 12 of the workpiece 10 can be omitted.

[0060] As non-functional dead material, for example, a short-circuiting ring or a laminated core of a rotor also come into question.

[0061] The device according to FIGS. 3 and 4 is based on the same principle as the device according to FIGS. 1 and 2.

[0062] Instead of the grinding disk 23, however, the machining means 21 is designed as a grinding belt 24. The grinding belt 24 or the grinding unit 22 is, as illustrated in FIG. 1, arranged to be movable parallel to the axis of rotation 11. As an alternative, a plurality of grinding units 22 (each with a grinding belt 24 or grinding disk 21) may be provided, so that the balancing body 12 can be machined at the same time. A further difference with respect to the device according to FIG. 1 consists in the fact that the clamping unit 30 comprises a centering spindle 33, so that so that the bearing seats 32 of the workpiece 10 can be machined. Consequently, the grinding unit 22 has a multiple function. As described in conjunction with FIG. 1, the grinding unit 22 makes it possible to reduce the unbalance by material removal. Furthermore, in addition the bearing seats 32 can be machined, as a result of which overall the efficiency of the device is improved.

[0063] The advancing movement of the machining means 21 is not effected by a movement of the grinding unit 22, but by a tilting movement of the clamping unit 30 (see double-headed arrow according to FIG. 4). This achieves a reduction in the spacing between the axis of rotation 11 and the grinding belt 24.

[0064] With respect to the rest of the features of the device, reference is made to the statements in conjunction with FIGS. 1 and 2.

[0065] The devices according to FIGS. 1 to 4 function e.g. as follows (method):

[0066] The workpiece 10 is clamped into the clamping unit 30 and rotated about the axis of rotation 11. The rotary drive 13 is provided for this purpose. One or more sensors measure the forces and/or torques and/or oscillations that result on account of the unbalance of the workpiece 10 during the rotation. To reduce the unbalance, during the measurement operation the material of the workpiece 10 is removed (directly or via the balancing body or the balancing bodies 12). The removal is effected by grinding. Other material removing methods are possible.

[0067] As an alternative to the simultaneous measurement and correction, it is possible that the measuring and material removal are effected separately in terms of time. In this case, the workpiece 10 continues to continuously rotate between these two operations.

[0068] FIG. 7 schematically illustrates a rotor 50. The rotor has a shaft 40, a laminated core 41 and two balancing disks 43. The balancing disk is magnetically inactive and consists customarily of iron. During the balancing operation, the magnetically active part of the rotor (rotor laminated core, magnets or winding) is separated from the balancing disk 43 by a shielding element 45. For balancing, material is removed at at least one of the balancing disks 43 according to one of the abovementioned methods. In this case, the balancing disk can be ground in a nonround manner over the circumferential face (A2). As an alternative, it is possible to machine the balancing disk at the face side (A1) by axially advancing a machining means.

[0069] FIG. 8 schematically illustrates a rotor 51 corresponding to FIG. 7. In contrast to FIG. 7, the rotor has a squirrel cage with short-circuiting bars 44 and short-circuiting rings 42. A short-circuiting ring is the end-side electric connecting element of a squirrel cage in an asynchronous machine. The squirrel cage may be cast or assembled (from short-circuiting bars and short-circuiting rings). The short-circuiting bars 44 finish flush with the short-circuiting rings 42. Axially, they do not reach beyond the short-circuiting rings. A shielding element 45 is attached to protect the laminated core from grinding dust or the like. The rotor does not have any balancing disks. For balancing, material is removed at at least one of the short-circuiting rings 42 according to one of the abovementioned methods. In this case, the short-circuiting ring 42 can be ground in an nonround manner over the circumferential face (B2). As an alternative, it is possible to machine the short-circuiting ring 42 at the end side (31) by axially advancing a machining means.

[0070] FIG. 9 schematically illustrates a rotor 50 corresponding to FIG. 7. In contrast to FIG. 7, for the purposes of balancing the rotor is machined at the circumferential surface (C) of the laminated core. Here, the laminated core as such is ground in a nonround manner. This may be used particularly advantageously for asynchronous machines with cast squirrel cages, since, in the case of cast squirrel cages, the laminated core has to be post-machined in any case on account of casting residues swelling out between sheet-metal laminations of the laminated core. Here, too, a separate balancing disk can be dispensed with.

LIST OF REFERENCE SIGNS

[0071] A1, A2, B1, B2, C Machining positions for balancing [0072] 10 Workpiece [0073] 11 Axis of rotation [0074] 12 Balancing body [0075] 13 Rotary drive [0076] 20 Machining unit [0077] 21 Machining means [0078] 22 Grinding unit [0079] 23 Grinding disk [0080] 24 Grinding belt [0081] 30 Clamping unit [0082] 31 Bearing means [0083] 32 Shaft seat [0084] 33 Centering spindle [0085] 40 Rotor shaft [0086] 41 Rotor laminated core [0087] 42 Short-circuiting ring (of an asynchronous machine) [0088] 43 Balancing disk/balancing body [0089] 44 Short-circuiting bars [0090] 45 Shielding element [0091] 50 Rotor (of an electric machine) [0092] 51 Rotor (of an asynchronous machine)