WO2001069095A2 - Device and method for balancing a shaft while said shaft rotates - Google Patents

Abstract

The invention relates to a device for balancing a shaft (1) by removing material while said shaft (1) rotates. The inventive device comprises a laser source (2) for impinging upon the shaft (1) with a laser beam (3, 4, 5) and a control and regulating device (6) for activating the laser source (2) for emitting the laser beam (3, 4, 5) for removing material on the shaft (1). The invention also relates to a method for balancing a shaft by removing material while said shaft rotates. The position of at least one balancing point on the shaft is detected and a laser source is correspondingly activated for impinging upon the rotating shaft for removing material on the detected balancing point.

Description

Device and method for balancing a shaft while the shaft is rotating

DESCRIPTION

The invention relates to a device for balancing a shaft by material removal during the rotation of the shaft and an associated method for balancing a shaft.

It is known that in the manufacture of high-speed shafts or rotors, manufacturing inaccuracies occur, which results in an asymmetrical mass distribution with respect to the axis of rotation and often considerable unbalance forces occur on the bearings at higher speeds. These unbalanced forces can damage the bearings or impair the functionality of the entire machine.

Suitable and known measuring devices must first be used to determine the unbalance position on the shaft circumference. Thereupon, according to a first method for balancing, by applying weights (for example screws, build-up welding, etc.), the unbalanced mass can be compensated for in relation to the determined unbalance position. According to a second method of balancing, the unbalance mass is removed directly at the unbalance position by material removal (e.g. by filing, milling, drilling, etc.). According to a third method of balancing, weights are attached to the shaft, which change their distance from the axis of rotation of the shaft and thus allow the unbalance forces to be compensated. This The method is mainly used in automatic balancing devices and can only be used at low speeds.

In the above-mentioned first and second methods for balancing high-speed shafts, the shaft must be stopped to compensate for or remove the unbalance and, after balancing has been carried out, it must be brought back up to the operating speed for assessing the balancing success. Since cooling occurs during the time the shaft stops, it is often necessary to wait until the operating or steady-state temperature is reached again, especially when the balancing quality is high, after the motor has been restarted.

This process of stopping and restarting the shaft generally has to be repeated several times in a complete balancing process, depending on the required balancing quality, as a result of which considerable time and production costs are incurred.

The invention is based on the object of offering a device for balancing in which material removal for balancing the shaft is made possible during the rotation of the shaft. Furthermore, a method for operating such a device is to be offered.

This object is achieved by the features of patent claim 1. Advantageous embodiments of the device are described in claims 2-12. For the method, the object is achieved by the features of patent claim 13. Advantageous method variants are described in claims 14-26. The device according to the invention for balancing a shaft by removing material during the rotation of the shaft comprises a laser source for applying a laser beam to the shaft and a control and / or regulating device for activating the laser source for temporarily emitting the laser beam for material removal at a determined unbalance position (balancing point). on the shaft. The laser source has sufficient output power to cause material removal at the respective balancing point in the short period of a shaft revolution.

In order to achieve sufficient output power, pulsed lasers are used in particular for material processing (Kneubühl, F.K.-Sigrist, M.W., Laser, 1999, Teubner, Stuttgart, pp. 187 ff).

A pulsed laser does not work in continuous pulse mode, since this would produce a uniformly distributed circumferential groove on the shaft surface and, as desired, material would not be removed locally at a balancing point within a balancing angle. For this reason, the laser beam is modulated to generate a balancing pulse within a balancing pulse duration. This balancing pulse duration is shorter than the period of a shaft revolution, the balancing pulse of the laser beam emitted during the balancing pulse duration being composed of a series of a plurality of individual laser pulses.

In an advantageous embodiment, at least one sensor for determining unbalance data of the rotating shaft (for example a distance sensor for determining a wobbling movement) is provided on the device according to the invention. In addition, at least one Accelerometers for determining further vibration frequencies of the shaft can be provided in certain planes.

Furthermore, the device according to the invention can have a Hall sensor for determining the rotational frequency of the shaft. By combining all the sensor data, one or more unbalance positions (balancing points) on the shaft can be determined in a manner known per se.

According to the invention, the laser pulse of the laser source can be correspondingly modulated by a modulation device, e.g. to be able to change the phase position and the balancing pulse duration of the laser beam.

The laser pulses or laser beams emitted by the laser source are focused at the determined balancing point via waveguides and optical devices known per se (decoupling optics).

The data of the sensor for determining unbalance data of the shaft, the acceleration sensor and / or the Hall sensor are advantageously processed via a measuring amplifier and / or an evaluation device for processing measured variables is connected to the control and / or regulating device.

In a particularly advantageous embodiment, a laser source is designed to emit first laser beams to remove material from the shaft and to emit at least one second laser beam for reflection as a test beam on at least one mirror element attached to the shaft. Such a device is particularly suitable for optical spindles with at least one mirror element, for example for laser processing. Projection at a shaft end, as are known, for example, from the GMN brochure 2509 04 ^ 00 "GMN Opto-Spindles". The waves accommodated in such optical spindles have at least one mirror element, for example a pentaprism, or several mirror elements attached in the peripheral regions of a shaft shoulder Reflection of a laser beam, for example for image projection.

When installing such a shaft in an optical spindle according to the specified GMN brochure, optimal projection properties of the mirror element (s) are aimed for.

In this case, at least one first laser beam emits material on the shaft to improve the balance quality of the shaft and, during the shaft rotation and during material removal, a second laser beam is used to determine whether the desired optimal projection properties are also achieved. The balance quality and directly the projection quality of the shaft with attached mirror element can be determined indirectly by evaluating the reflected test beam.

If the material removal due to the first laser beam detects a deterioration in the projection quality when evaluating the test beam, this can be compensated for by appropriate control or regulation of the first laser beam by an additional, additional material removal.

The second laser beam can be an attenuated laser beam from the first laser source or can come from a separate second laser source (for example a laser diode). The balance quality and furthermore the projection quality of the shaft with mirror element can be determined indirectly in one work step via an acquisition element for evaluating the reflected test beam - isolated or in connection with other described sensors. In this way, all properties that are essential for the shaft of an optical spindle (such as mechanical quality, for example balancing quality and optical quality, for example projection quality) can be determined in one operation. Such a device thus serves not only for balancing the shaft with a mirror element, but also for optimizing the projection quality of such a shaft. The method according to the invention for this is also described in connection with the drawing figures.

In the method according to the invention for balancing a shaft by removing material during the rotation of the shaft, the position of at least one balancing point on the shaft is first determined (step 1) in order then to achieve a desired material removal during the rotation of the shaft by activating the laser source accordingly (2nd step).

These two steps can be carried out several times in succession and linked together in the manner of a control loop.

A pulsed laser source with an additional modulated laser beam is used. By selecting and / or changing the balancing pulse duration and phase position (phase angle) of the balancing pulse of the laser beam within the balancing period of the laser beam, the desired material removal to reduce and ultimately eliminate the unbalance of the shaft can be achieved during rotation of the shaft at the determined balancing point. The decreasing imbalance of the shaft can continue during the rotation of the shaft can be determined by the existing sensors and, by appropriately controlling the laser source via the control and / or regulating device, an adaptive adaptation of the laser pulse or the laser beam emitted by the laser source until finally the ascertained unbalance within a closed control loop is completely eliminated be performed.

Further details of the method according to the invention and of the device can be seen from the exemplary embodiments in the drawing figures. Show it:

Fig. 1 is a schematic representation of the invention

Device for balancing a shaft with a laser source,

2 is a view A of the shaft of FIG. 1,

3 shows a first representation of the balancing pulse of the laser beam,

4 shows a further representation of the balancing pulse of the laser beam,

Fig. 5 is a schematic representation of an embodiment of the device according to the invention for balancing a shaft with two laser beams and

6 is a view B of the shaft of FIG .. 5 Fig. 1 shows a fast rotating shaft 1, with a rotational frequency f _w between about 0.5 - 3 kHz. At the end of the shaft 1, a shaft shoulder 21 is attached. A polygon mirror can be attached to the shaft shoulder 21, for example, on the circumference, in order for the shaft to be installed later

I emit laser beams into a laser projection system for projection onto an image surface. The shaft 1 is received in a bearing 7 and is driven by a motor 24 (synchronous motor). The rotational frequency f _{w of} the shaft 1 is measured via a Hall sensor 11, which is attached in the vicinity of the motor 24. Accelerometers 8, 9 are attached to the bearing 7 and determine the respective oscillation frequencies occurring due to the unbalance of the shaft 1 in two planes. By combining the data from the Hall sensor 11 and the acceleration sensors 8, 9, the phase position of the unbalance oscillation and thus the location of the unbalance on the shaft circumference, that is to say the unbalance position or balancing points 18, 19 and / or 20 on the shaft 1, can be determined. In addition, the data from the sensor 10, which detects a wobbling movement of the shaft shoulder 21, can be incorporated in the determination of the unbalance position (s).

The accelerometers 8, 9, the sensor 10 and the Hall sensor

II are connected to a measuring amplifier 16 for processing the respective sensor data. The location of balancing points 18, 19 and / or 20 can be determined in a manner known per se via the recorded data of the sensors mentioned. In the following, the data of the measuring amplifier 16 are processed by the evaluation device 17 and measured variables for controlling the control and / or regulating device 6 are generated. The latter is used to control the modulation device 12, whereby the laser beams 3, 4, 5 are generated starting from the laser pulse 13 of the laser source 2 (eg CO 2 laser). By changing the Balancing pulse duration Δtj, the balancing period Tj and the phase angle Δα of the time of application of the balancing pulse (see FIGS. 3 and 4), the laser beams 3, 4, 5 are adjusted accordingly in order to achieve that the laser beams 3, 4 and / or 5 of the laser source 2 bring about the desired material removal at the determined balancing points 18, 19 and / or 20 to eliminate the imbalance determined.

After passing through the modulation device 12, the laser pulse 13 is brought to the shaft 1 via the waveguide 14 and optical devices 15 (coupling optics) known per se.

By activating the laser source 2 and modulation device 12, the laser beams 3, 4 and / or 5 are applied once or repeatedly to the balancing points 18, 19 and / or 20 on the shaft 1 and / or the shaft shoulder 21.

A reduction in the unbalance of the shaft 1 by the attached sensors 8, 9, 10 and / or 11 is determined by the material removal that occurs due to the impingement of the laser beams 3, 4 and / or 5. A closed control circuit can be present via the sensors 8-11, the measuring amplifier 16, the evaluation device 17, the control and / or regulating device 6 and the modulation device 12. According to the invention, the detected imbalance can thus be automatically eliminated when the shaft 1 rotates.

FIG. 2 shows a view A of the shaft shoulder 21 with a balancing point 20 within the balancing angle φ. The balancing point 20 extends flatly within the balancing angle φ over a partial region of the ring surface 22 with the width 23. By appropriate activation of the laser source 2 and modulation of the laser pulse 13, it is achieved that the laser beam 5 acts on the shaft shoulder 21 only in the area of the balancing point 20, so that in this area alone the determined unbalance is removed by material removal.

Further details on the activation of the laser source 2 can be seen from the illustrations in FIGS. 3 and 4. 3 shows a single laser pulse with the balancing period Tj. The laser source 2 is pulsed in a modulated manner within the balancing pulse duration Δtj, so that a balancing pulse with an increased intensity I is produced, which leads to material removal on the shaft 1.

According to the method according to the invention, the balancing period Tj of the laser beam and the period T _{w of} a shaft revolution or the associated balancing frequencies fj = Tj ^{" 1} and f _w = T _w ^{" 1 are to} be coordinated with ^one another.

According to a first method variant, the balancing frequency fj of the laser beam and the rotational frequency f _{w of} the shaft match. Since the material removal of the laser beam occurs only during a balancing pulse duration Δtj and applies to Δtj <Tj, only a partial circumference of the shaft is thus acted upon by the laser beam, for example in the area of the balancing angle φ of the shaft according to FIG. 2.

According to a second method variant, the rotational frequency f _{w of} the shaft can be an integral multiple of the balancing frequency fj des Laser beam amount, whereby it is achieved that material removal does not take place with each shaft revolution and material removal that is too fast or uncontrollable is avoided.

In an advantageous method variant, the balancing pulse duration Δtj of the laser beam is at most about 65% of the balancing period Tj of the laser beam pulse. If the balancing pulse duration Δtj of the laser beam is approximately 20% of the balancing period Tj of the laser beam pulse, a particularly precise material removal can take place on the shaft.

A particularly high balancing quality results if the balancing pulse duration Δtj of the laser beam is at least about 0.8% and at most about 70% of the period T _{w of} a shaft revolution.

A further optimization of the balancing quality is achieved if the product of the rotational frequency f _{w of} the shaft, the balancing pulse duration Δtj of the laser beam and the balancing angle φ is at most about 100 angular degrees. A particularly high-quality balancing is achieved if the product mentioned is approximately 60 degrees.

Overall, the result is that the unbalanced masses at the balancing point found are eliminated by a minimum of material removal, in order not to cause a weakening of the strength of the shaft and an associated undesired deformation.

When balancing effectively, it is important to remove the unbalanced masses by removing a minimum of material in order not to weaken the strength. cause the balanced body and a related deformation. Considerable centrifugal forces and gyroscopic moments act in the fast-rotating shaft, which creates such elastic deformations that often occur as bending deformation and, due to their asymmetry, lead to a speed-dependent balance quality. This means that the entire speed range of the shaft can only be properly balanced for a small speed window. Otherwise, speed ranges with significant unbalance are passed through.

The above relationships of the individual parameters for optimizing the laser beam serve overall to improve and optimize the balance quality.

It should also be noted that a very small balancing angle φ and thus punctiform material removal by the laser beam is also undesirable since the actual unbalanced masses are regularly distributed over the surface of the shaft at the balancing points.

A point-like removal of material by the laser beam would lead to asymmetrical elastic deformations and thus to an undesired speed-dependent balancing quality.

As shown, the existing balancing points are determined in a manner known per se by the sensor system shown in FIG. 1 with the sensors 8-11. Based on the evaluation of this sensor data, the phase position of the laser beam can be determined within the balancing period Tj, that is to say the phase angle Δα of the point in time at which the balancing pulse of the laser beam is used. Since a direct match between the phase position of the balancing pulse and the phase position of the unbalance position can rarely be achieved, the phase position of the unbalance must be limited from both sides by the phase position of the balancing pulse.

For this purpose, the phase angle Δα of the time of use of the balancing pulse is changed within the balancing period Tj of the laser beam. The change steps must not be chosen too small, since the measurement results of the sensors are subject to fluctuations that are caused by measurement inaccuracy, processing errors in the measuring amplifier, thermal influences on the bearing of the shaft, etc.

If the change in the phase angle Δα is too small, a wrong direction of the change in the phase position can be embarked on, as a result of which an undesirable increase in the unbalance can even occur.

On the other hand, the change steps of the phase angle Δα must not be chosen too large, since this places the locations at which the laser beam strikes the shaft at a distance from one another. Excessive changes in the phase angle Δα lead to undesired, spaced, point-like material removals on the shaft. In this context, the phase angle Δα is changed in steps of a maximum of approximately Δα = 120 angular degrees in an advantageous method variant (cf. FIG. 4).

FIG. 5 shows a schematic representation of a device according to FIG. 1, wherein all elements, devices and sensors shown in FIG. 1 can also be present in a device according to FIG. 5. To illustrate the essential functional principle of the device according to FIG. 5, the laser source 2 and the shaft 1 received in the bearing 7 and driven by the motor 24 are shown for better clarity.

The shaft 1 is intended for later installation in a laser projection system in accordance with the GMN brochure mentioned in the description and has at least one mirror element 27, e.g. a pentaprism or - as shown in FIGS. 5 and 6 - a total of eight mirror elements 27. When the laser source 2 is activated, the material is removed by the laser beam 5 at the shaft shoulder 21. At the same time, a weakened laser beam 25 e.g. reflected from the laser source 2 on a mirror element 27 of the shaft 1 and fed as a reflection beam 29 to a detection element 28.

Thus, the reflection and projection properties of the mirror elements 27 of the shaft 1 can be detected simultaneously in one operation during the removal of material and the improvement of the balancing quality by impinging the laser beam 5. In this way, in addition to balancing the shaft 1 intended for an optical spindle, the projection properties of the shaft 1 can also be improved.

The second laser beam 25 can originate from the laser source 2 or from a further laser source 26 (e.g. a laser diode). The detection element 28 can be designed as a PSD sensor.

If the device according to FIG. 5 is equipped with a Hall sensor 11 and acceleration sensors 8, 9 according to FIG. 1, the Hall sensor 11, the acceleration sensors 8, 9 and / or the Detection element 28 are determined in a joint evaluation of the data obtained there, whether the shaft 1 has a sufficient balance quality and at the same time sufficient and optimized projection properties.

A device according to FIG. 5 and a method for operating such a device thus serve to balance a shaft 1 for an optical spindle and to simultaneously determine and improve the projection quality of the mirror elements 27 of the shaft 1.

In a further embodiment, the laser beam 5 can be generated solely by the further laser source 26, only the laser beam 5 for material removal on the shaft 1 being produced in the laser source 2.

In the detection element 28, which is preferably designed as an optical sensor, a change in location of the reflection beam 29, e.g. can be determined on the basis of a geometric change of at least one mirror element 27 during the balancing of the shaft 1.

FIG. 6 shows a view of the shaft 1 from direction B according to FIG. 5, a first balancing point 30 and a second - deepened or expanded - balancing point 31 being depicted on the shaft 1.

If material is removed at the balancing point 31 by the incident laser beam 5, a geometric shift of the mirror element 27 into the position of the mirror element 27 ′ can occur, which is detected by a local change in the reflection beam 29 in the direction 32 of the laser beam 25 in the detection element 28 according to FIG. 5 becomes. Thus, the method according to the invention and the device according to the invention can also be used to improve material removal changes in the reflection properties occurring in the balance quality are determined and a shaft 1 with a high balance quality and optimized projection properties can be produced.

Claims

PATENT CLAIMS Device for balancing a shaft (1) by removing material during the rotation of the shaft (1) a laser source (2) for applying a laser beam (3, 4, 5) to the shaft (1) and a control and / or regulating device (6) for activating the laser source (2) for emitting the laser beam (3, 4, 5) for material removal on the shaft (1). Apparatus according to claim 1, wherein at least one sensor (10) is provided for determining unbalance data of the shaft (1). Apparatus according to claim 2, wherein the sensor (10) is provided for detecting a wobbling movement of the shaft (1). Device according to one of claims 1-3, wherein at least one acceleration sensor (8, 9) is provided for determining an oscillation frequency of the rotating shaft (1). Device according to one of claims 2-4, wherein a Hall sensor (11) for determining the rotational frequency fw of the shaft (1) is provided. Device according to one of claims 1-5, wherein a modulation device (12) for modulating a laser pulse (13) of the laser source (2) is provided. Device according to one of claims 1-6, wherein at least one waveguide (14) and at least one optical device (15) is provided to act upon the rotating shaft (1) with the laser beam (3, 4, 5). Device according to one of claims 2-7, wherein the acceleration sensor (8, 9), sensor (10) and / or hook sensor (11) via a measuring amplifier (16) and / or an evaluation device (17) with the control and / or Control device (6) is connected. Device according to one of the preceding claims, wherein the laser source (2) for emitting first laser beams (3, 4, 5) for material removal on the shaft (1) and for emitting at least one second laser beam (25) for reflection as a test beam on at least one the shaft (1) attached mirror element is formed. Apparatus according to claim 9, wherein instead of the laser source (2) a further laser source (26) for emitting the second laser beam (25) for reflection as a test beam is provided on at least one mirror element attached to the shaft (1). Apparatus according to claim 9 or 10, wherein the signal quantities of the first laser beam (3, 4, 5) and of the second laser beam (25) can be set separately and differently. Device according to one of claims 9-11, wherein the laser beam (25) reflected on at least one mirror element of the shaft (1) is fed to a detection element (26) for evaluation. A method for balancing a shaft by removing material during the rotation of the shaft, in particular a method for operating a device for balancing a shaft with the features of claims 1-12, wherein the position of at least one balancing point on the shaft is determined and A corresponding activation of a laser source for applying the rotating shaft with a laser beam for material removal takes place at the determined balancing point. The method of claim 13, wherein the position of the balancing point on the shaft is determined by evaluating at least one sensor. The method of claim 13 or 14, wherein the balancing frequency fj of the laser beam for material removal on the shaft coincides with the rotational frequency fw of the shaft. Method according to one of claims 13 or 14, wherein the rotational frequency f of the shaft is an integral multiple of the balancing frequency fj of the laser beam. Method according to one of claims 13 - 16, wherein the balancing pulse duration Δtj of the laser beam is at most about 65% of the balancing period Tj of the laser beam. The method of claim 17, wherein the balancing pulse duration Δtj of the laser beam is approximately 20% of the balancing period Tj of the laser beam. Method according to one of claims 13 - 18, wherein the balancing pulse duration Δtj of the laser beam is at least about 0.8% and at most about 70% of the period T _{w of} a shaft revolution. Method according to one of claims 13 - 19, wherein the product of the rotational frequency fw of the shaft, balancing pulse duration Δtj des Laser beam and balancing angle φ on the shaft is at most about 100 degrees. The method according to claim 20, wherein the product of the rotational frequency fw of the shaft, the balancing pulse duration Δtj of the laser beam and Balancing angle φ on the shaft is approximately 60 degrees. Method according to one of claims 13 - 21, wherein the phase angle Δα of the time of use of the balancing pulse of the laser beam is changed within the balancing period Tj of the laser beam. The method of claim 22, wherein the phase angle Δα is changed in steps of at most about 120 degrees. Method according to one of claims 13-23, wherein a first laser beam for acting on the rotating shaft for material removal and a second laser beam for reflection are emitted on at least one mirror element of the shaft for checking the reflection quality. The method of claim 24, wherein the second laser beam reflected by the wave is evaluated in a detection element. The method of claim 24 or 25, wherein the first laser beam and the second laser beam have different signal sizes and can be set separately.