METHOD FOR ACTIVELY BALANCING A ROTOR, AND DEVICE COMPRISING A ROTOR AND A MECHANISM PAIRED WITH THE ROTOR FOR ACTIVELY BALANCING SAME

Abstract

The invention relates to a method for actively balancing a rotor (1), comprising: providing a device with a rotor (1) that can be rotated around an axis of rotation and a mechanism (2) allocated to the rotor (1) for actively balancing, in which a magnetic fluid (7) is received in a fluid chamber (6) formed on the rotor (1), which partially fills the fluid chamber (6) and contains at least one of the following fluids: ferrofluid and magnetorheological fluid; holding the magnetic fluid (7) by means of a permanent magnetic field of a permanent magnet (5) arranged on the rotor (1) in an initial position in the fluid chamber (6); rotating the rotor (1) around the axis of rotation (3), and passing the fluid chamber (6) and permanent magnet (5) by an electrical exciter system with a fixedly arranged electromagnet (8) during the rotation of the rotor (1), wherein the permanent magnetic field of the permanent magnet (5) and an electromagnetic field of the electromagnet (8) here overlap in an activated state for active balancing purposes, so that the magnetic fluid (7) in the fluid chamber (6) performs a mass displacement proceeding from the initial position. Also created is a device with a rotor (1) and a mechanism (2) allocated to the rotor (1) for actively balancing the rotor (1).

Claims

1. A method for actively balancing a rotor comprising: providing a device with a rotor rotatable around an axis of rotation and a mechanism assigned to the rotor for actively balancing, in which a magnetic fluid is received in a fluid chamber formed on the rotor which partially fills the fluid chamber and contains at least one of the following fluids: ferrofluid and magnetorheological fluid; holding the magnetic fluid by means of a permanent magnetic field of a permanent magnet arranged on the rotor in an initial position in the fluid chamber; rotating the rotor around the axis of rotation; and passing the fluid chamber and the permanent magnet by an electrical exciter system with a fixedly arranged electromagnet during the rotation of the rotor, wherein the permanent magnetic field of the permanent magnet and an electromagnetic field of the electromagnet here overlap in an activated state for active balancing purposes, so that the magnetic fluid in the fluid chamber performs a mass displacement proceeding from the initial position.

2. The method according to claim 1, characterized in that the magnetic fluid is shifted in at least one of the following directions during mass displacement: radial direction and tangential direction.

3. The method according to claim 1, characterized in that the magnetic fluid performs the mass displacement based upon a radial acceleration, which acts on the magnetic fluid during the rotation of the rotor.

4. The method according to claim 1, characterized in that, during the rotation of the rotor, the magnetic fluid performs the mass displacement based upon a resulting magnetic field, which arises due to the overlap of the permanent magnetic field and the electromagnetic field.

5. The method according to claim 1, characterized in that, due to the mass displacement of the magnetic fluid during the rotation of the rotor, at least one of the following mass balancing processes is performed: a positive mass balancing and negative mass balancing.

6. The method according to claim 1, characterized in that the fluid chamber is partially filled with a magnetic fluid, which consists of the magnetorheological fluid.

7. The method according to claim 1, characterized in that the magnetic fluid in the fluid chamber flows back if a rotational speed of the rotation of the rotor is reduced.

8. The method according to claim 1, characterized in that the magnetic fluid is held by means of the permanent magnetic field in the initial position on an inner side of the fluid chamber lying inside in radial direction; and during the rotation of the rotor for active balancing purposes, is displaced from the inner side partially towards an outer side of the fluid chamber lying outside in radial direction.

9. The method according to claim 1, characterized in that, during the rotation of the rotor, a change is be made between various stable system states, which each are maintained by means of the permanent magnetic field of the permanent magnet and/or the radial acceleration acting on the magnetic fluid, wherein the various stable system states have a respectively different distribution of the mass of the magnetic fluid in the fluid chamber.

10. The method according to claim 1, characterized in that several segmented areas are formed on the rotor, which each consist of an assigned permanent magnet and an assigned fluid chamber with magnetic fluid.

11. The method according to claim 1, characterized in that the permanent magnet is formed on the rotor by means of a ring magnet.

12. The method according to claim 1, characterized in that the electrical exciter system is formed with several electromagnets, which each are oppositely and fixedly arranged in relation to the rotor, and past which the fluid chamber is guided during the rotation of the rotor, such that the permanent magnetic field and the electromagnetic field of the electromagnet each overlap in an activated state for active balancing purposes.

13. A device with a rotor and a mechanism assigned to the rotor for actively balancing the rotor, further comprising: an axis of rotation around which the rotor is rotatable; a fluid chamber that is arranged on the rotor; a magnetic fluid, which partially fills the fluid chamber and contains at least one of the following fluids: ferrofluid and magnetorheological fluid; a permanent magnet, which is arranged on the rotor and configured to hold the magnetic fluid in an initial position in the fluid chamber by means of a permanent magnetic field; and an electrical exciter system with a fixedly arranged electromagnet, such that, during the rotation of the rotor, when the fluid chamber and the permanent magnet are bypassable the electromagnet, the permanent magnetic field of the permanent magnet and an electromagnetic field of the electromagnet overlap in the activated state for active balancing purposes, so that the magnetic fluid in the fluid chamber can perform a mass displacement proceeding from the initial position.

Description

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0041] Additional exemplary embodiments will be explained below with reference to the figures of a drawing. Shown here on:

[0042] FIG. 1 is a schematic view of a device with a rotor and a mechanism for actively balancing by radially displacing a magnetic liquid;

[0043] FIG. 2 is a schematic view of an additional device with a rotor and a mechanism for actively balancing by tangentially displacing a magnetic liquid;

[0044] FIG. 3 is a schematic view of another device with a rotor and a mechanism for actively balancing by way of a positive or negative mass balance;

[0045] FIG. 4 is a schematic, perspective view of a rotor, in which a fluid chamber with a magnetic liquid is arranged in rotor elements, wherein the latter is held on the inside in an initial position;

[0046] FIG. 5 is a schematic, perspective view of the rotor from FIG. 4, wherein the magnetic liquid is partially displaced outwardly in a radial direction;

[0047] FIG. 6 is a schematic, perspective view of the rotor from FIG. 4, wherein the magnetic liquid in the fluid chamber has been completely displaced to a radially outer lying outer side of the fluid chamber;

[0048] FIG. 7 is a schematic, sectional view of a rotor element of the rotor from FIG. 4 at different times of a rotational movement of the rotor;

[0049] FIG. 8 is a graphic view of the current flow of an electromagnet as a function of time, as well as of an imbalance UMRF resulting from a displacement of the magnetic liquid, which can be used for compensating an imbalance that is present in the initial state of the system;

[0050] FIG. 9 is a schematic view of a device with a rotor and an allocated fixed electromagnet;

[0051] FIG. 10 is a schematic view for the sequence of a balancing process;

[0052] FIG. 11 is a schematic view for results of the sequence of an automated, active balancing; and

[0053] FIG. 12 is a schematic view of a device with a rotor and a mechanism for actively balancing by radially displacing a magnetic liquid using several oppositely polarized permanent magnets.

[0054] FIG. 1 shows a schematic view of a device with a rotor 1 and a mechanism for balancing 2 allocated to the rotor 1. The rotor 1 can be rotated around a rotational axis 3. Three segmented areas 4 are circumferentially arranged on the rotor 1, which each have a permanent magnet 5 and an allocated fluid chamber 6 with a magnetic liquid 7, which partially fills the fluid chamber 6. In other embodiments, more than three segmented areas 4 can be provided.

[0055] Electromagnets 8 are allocated opposite the rotor 1, and can be exposed to an electrical current to form an electromagnetic field, whether it be pulsed in time intervals, in particular in cases where one of the fluid chambers 6 is passed by the electromagnet, or permanently during the rotation of the rotor 1. An overlapping of a permanent current with time limited pulses can here be provided. The fluid chamber 6 of the segmented areas 4 is designed as a closed chamber for receiving the magnetic liquid 7.

[0056] The magnetic liquid 7 is held on an inner side 9 lying inside in radial direction with the help of the permanent magnet 5. This is caused by a permanent magnetic field provided by means of the permanent magnet 5, which acts on the magnetic liquid 7. The magnetic liquid 7 can comprise at least one of the following liquids: ferrofluid and magnetorheological liquid. In one configuration, the magnetic liquid 7 consists exclusively of the magnetorheological liquid.

[0057] If the rotor 1 is made to rotate, the segmented areas 4 are each passed by the electromagnet 8. For example, the electromagnets 8 can then be exposed to an electrical current (current pulses) corresponding to a cycled operation, so that they each provide an electromagnetic field. If one of the electromagnets 8 is exposed to an electrical current, the permanent magnetic field of the allocated permanent magnet 5 is superposed with the electromagnetic field of the opposing electromagnets 8 for one or several of the segmented areas 4, so that a resulting magnetic field comes about for the magnetic liquid 7 in the fluid chamber 6. The electromagnetic field here at least partially compensates for the permanent magnetic field, wherein an overcompensation can also be provided. It can also be provided that the electromagnetic field does not compensate for the permanent magnetic field, but instead strengthens it.

[0058] During the rotation of the rotor 1 around the axis of rotation 3, a mass displacement of the magnetic liquid 7 to a radially outer lying outer side 13 of the fluid chamber 6 takes place in the segmented areas 4 during exposure to the electromagnetic field of the electromagnet 8. The magnetic liquid 7 here flows partially to the outer side 13, so as to actively balance in this way. One part 14 of the magnetic liquid 7 remains on the inside, while another part 15 of the magnetic liquid 7 flows radially outward. The mass displacement that can be induced for one or several of the segmented areas 4 by means of the electromagnet causes a change in mass distribution for the rotor 1 when the latter is rotated.

[0059] If the rotational speed of the rotor decreases 1, the part of the magnetic liquid 7 that flowed toward the outer side 13 of the fluid chamber 6 according to FIG. 3 can flow back radially inwardly, as a result of which another mass distribution is in turn formed on the rotor 1. This return movement can take place due to gravitation and/or the effect of the magnetic field generated by the permanent magnet 5 and/or the electromagnet 8.

[0060] In this way, the mass distribution on the rotor 1 can be controlled as a function of operation by individually activating the electromagnet(s) 8 during the rotation of the rotor 1. For activation purposes, a (pulsed) current i flows through the respective electromagnets 8.

[0061] In the depicted embodiments, the electromagnets 8 are fixedly arranged relative to the rotor 1, and thereby comprise a stationary electrical exciter system.

[0062] FIG. 2 shows a schematic view of an additional device with the rotor 1 and mechanism for active balancing 2. In the embodiment shown, a continuous fluid chamber 6 with the magnetic liquid 7 is formed around the rotor 1, and has allocated to it a circumferentially arranged permanent magnet 5. During the rotation of the rotor, the effect of the electromagnet 8 causes the magnetic liquid 7 to locally shift in a tangential direction, which ultimately leads to a mass displacement 12 of the magnetic liquid 7 in a radial direction.

[0063] FIG. 3 shows a schematic view of another device with the rotor 1 and mechanism for active balancing 2. Depending on the interaction between the permanent magnetic field and the electromagnetic field, a positive mass compensation (positive mass displacement) can take place, as schematically shown on FIG. 1 with reference number 10. If the electromagnetic field at least partially compensates for the permanent magnetic field, a negative mass compensation (negative mass displacement) can take place, as schematically shown on FIG. 10 with reference number 11. The magnetic liquid 7 is here displaced toward the permanent magnet 5 due to the radial acceleration and/or resulting magnetic field.

[0064] FIGS. 4 to 6 show schematic, perspective views of a rotor 20 with three rotor elements 21, on which the respective fluid chamber 6 with the magnetic liquid and the allocated permanent magnet 5 are arranged. FIG. 4 shows the initial position for the magnetic liquid 7, which is arranged on the inner side (interior) 9 of the fluid chamber 6, and is held there by means of the permanent magnet 5. During the rotation of the rotor 20, the magnetic liquid 7 moves in the direction of the outer side 13 of the fluid chamber 6 according to FIGS. 5 and 6, which is controlled with the help of the allocated electromagnet(s) 8 (not shown on FIGS. 4 to 6) when the rotor elements 21 with the fluid chamber 6 are passed by the electromagnet and the electromagnet is activated.

[0065] FIGS. 7 and 8 show the above in more detail.

[0066] For a rotor element 21 that can be designed as a rotor blade, FIG. 7 shows a sectional view with the fluid chamber 6 and the magnetic liquid 7 arranged therein for various times t after the rotation of the rotor 20 has begun. It turns out that the magnetic liquid 7 is held on the inner side 9 at point in time t=0, and partially flows in a radial direction toward the outer side 13 with increasing time.

[0067] In this regard, FIG. 8 shows a graphic view of the pulsed current flow I.sub.EM for the electromagnet during the rotation of the rotor 20 as a function of time t. Also shown is the amount of imbalance UMRF resulting from the shifting of the magnetic liquid 7, which can be used to compensate for an imbalance present in the initial state of the system.

[0068] With reference to FIGS. 9 and 10, an automated active balancing process for the rotor 20 will be described below. These explanations apply accordingly to the rotor 1. FIG. 9 shows a schematic view of the rotor 20 with the rotor elements 21. The same reference numbers as on FIGS. 4 to 7 will here be used for the same features.

[0069] After the start of the balancing process (step 30), a present imbalance is determined and demodulated into amplitude u and phase φ.sub.u (step 31). Based on the determined phase angle, the fluid chamber 6a, 6b, 6c is selected in step 32. To this end, the phase position φ.sub.c=φ.sub.u+180° of a required correction mass to be provided via mass displacement of the magnetic liquid 7 is transferred into a body-fixed a, b, c-coordinate system (see FIG. 9). The corresponding segment (segmented area 4) in which the correction mass is supposed to lie is selected via a case differentiation according to equation (1.1). The specification of individual segments is shown on FIG. 9.

[0070] The following here applies:

[00001]$\begin{array}{cc}\begin{array}{c}\mathrm{Segment}\left({\phi }_c\right)=I\mathrm{for}0\le {\phi }_c<120,\mathrm{initial}\mathrm{axis}a\\ \mathrm{II}\mathrm{for}120\le {\phi }_c<240,\mathrm{initial}\mathrm{axis}b\\ \mathrm{III}\mathrm{for}240\le {\phi }_c<360,\mathrm{initial}\mathrm{axis}c\end{array}& \left(1.1\right)\end{array}$

[0071] The rotor elements 21, and thus the allocated fluid chambers 6a, 6b, 6c, extend along the axes a, b, c.

[0072] By determining the difference angle φ.sub.d between the angle of the correction mass φ.sub.c and the determined initial axis a, b or c of the segment, equation (1.2) and equation (1.3) can be used to calculate the corresponding ratio of the two fluid chambers 7, which border the segment and are offset by 120 degrees:

[00002]$\begin{array}{cc}{u}_1=\hat{u}.Math.\sin \left({\phi }_d\right).Math.\frac{2}{\sqrt{3}}& \left(1.2\right)\end{array}$$\begin{array}{cc}{u}_2=\hat{u}.Math.\left(\cos \left({\phi }_d\right)+\sin \left({\phi }_d\right).Math.\frac{1}{\sqrt{3}}\right)& \left(1.3\right)\end{array}$

[0073] For a correction mass in a first segment, the components u.sub.1 and u.sub.2 can be allocated to the fluid chambers 6a and 6b. For the other segments, allocation takes place according to the same principle.

[0074] Comparing the amounts of u.sub.1 and u.sub.2 makes it possible to identify a fluid chamber that corrects the imbalance most efficiently. The fluid chamber is correspondingly activated by the electromagnet 8, or the magnetic field of the permanent magnet 5 is compensated (step 33). The current I.sub.EM used for compensation is set by a separate regulator (not shown), which can incrementally increase the current from a starting value until the desired correction has been reached.

[0075] The described process is repeated until either the maximum current I.sub.EM,max has been reached and a continued increase in current produces no improvement, or the imbalance drops under the limit (steps 34, . . . , 37). In the first case, a sufficient balancing is not possible, while in the second case, the imbalance has been successfully corrected. In both cases, the process ends by virtue of the imbalance in a conditionally stable state, which can be maintained only through rotation and without any need for electrical energy.

[0076] FIG. 11 shows a schematic view for results from the course of an automated, active balancing process. As a result of the used sequence, fluid chamber 6b is initially identified as the most efficient option, and a corresponding mass shifting is performed. The latter is denoted by an arrow 40. After a specific mass of the magnetic liquid 7 has been shifted, the position of the resulting imbalance is shifted to an extent (phase position approx. 190°) that a more efficient correction can now be achieved with fluid chamber 6a (arrow 41).

[0077] Lastly, a phase position of approx. 300° is reached for the imbalance, and fluid chamber 6b must once again be activated (arrow 42 to midpoint). At the end of the illustrated progression, the set limit is dipped below, thereby resulting in a state that is stable and balanced during rotation.

[0078] It can be provided that the magnetic liquid 7 (also abbreviated as MRF on FIG. 11) be simultaneously shifted in two of the fluid chambers 6a, 6b, 6c. The information required for this purpose can be derived from equation (1.2) and (1.3). This makes it possible to approach the balanced state directly. This sequence is shown on FIG. 11 as arrow 43.

[0079] FIG. 11 shows the results of a balancing run with an initial imbalance of u.sub.Start=255 g mm (amplitude) at an angle of φ.sub.u,Start=262° (phase position) and a resulting imbalance u.sub.End=2.34 g mm at an angle of φ.sub.u,End=169°.

[0080] FIG. 12 shows a schematic view of another device with the rotor 1 and a mechanism for active balancing 2 according to the principle of radially displacing the magnetic liquid 7. As opposed to the exemplary embodiments illustrated above, an additional permanent magnet 40 is provided in the area of the radially outer lying outer side 13 of the fluid chamber 6. Other additional permanent magnets 40 can be provided.

[0081] The features disclosed in the above specification, claims and drawing can be important both separately and in any combination for realizing the various embodiments.