Rotor balancing device

Abstract

To provide a balancing device for a rotor.SOLUTION: A rotor 10 defines a rotation axis 10a. A balancing device 1 comprises a fixed portion 2 and a movable portion 3 for defining a central axis 3a. The movable portion 3 is constrained to the rotor 10 so that the central axis 3a substantially coincides with the rotation axis 10a and includes at least one eccentric mass 30 rotatable around the central axis 3a and not balanced with respect to the central axis 3a. The balancing device 1 further comprises movement means 4 for the eccentric mass 30. The movement means 4 includes a magnetic brake 40 and is suitable for rotating the eccentric mass 30 with respect to the rotor 10 around the central axis 3a.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a balancing device for a rotor of the kind specified in the preamble of claim 1 . [Background technology]

[0002] Currently, various rotor balancing devices are known.

[0003] Balancing devices are available that can constantly maintain the center of mass of a rotating part at a selected position, particularly for plate rotating devices in machine tools and other equipment. Typically, the center of mass of a rotating part is maintained relative to the axis of rotation, thereby preventing unintended centrifugal forces from being generated.

[0004] The balancing device generally includes an imbalance measuring means that is incorporated into the balancing mechanism and that is capable of determining and measuring the presence or absence of an imbalance.

[0005] As a result, the rotating part is constrained and the imbalance is regulated, eliminated or minimized by the balancing device.

[0006] The balancing device includes two unbalanced masses relative to the rotor's axis of rotation, each having a reasonably similar unbalance rather than being identical, and also includes a motor capable of rotating each mass about the axis of rotation itself, for a total of two motors.

[0007] The unbalanced mass position affects the center of mass of the rotating part.

[0008] In fact, if the masses are placed on opposite sides of the axis of rotation, offset by 180 degrees, the imbalances cancel each other out, so the balancing device does not change the mass center position of the assembly consisting of the rotor and the balancing device.

[0009] Conversely, if the masses are not opposite each other, their imbalances will not cancel each other out and an imbalance will also be created in the balancing device. At the same time, this imbalance is adjusted to be equal and opposite to the imbalance in the rotor, thereby correcting the position of the center of mass of the rotor / balancing device assembly so that it is along the axis of rotation or as close to the axis as possible.

[0010] The mass typically moves relative to the rotor and the central mass is modified by an electric motor and a mechanical connection, as described, for example, in commonly assigned US Pat.

[0011] On the other hand, Patent Document 2 shows a mass that is moved directly from a fixed part.

[0012] In commonly assigned US Pat. No. 5,629,999, a balancing mass is shown which is moved by a motor inside the mass itself.

[0013] In commonly assigned patent application WO 02 / 04999, a moving balancing mass is shown, which consists of a wire or tape that can be wound around a reel that is eccentric to the axis of rotation, so that by winding or unwinding it around different reels the mass can be moved and the center of mass of the balancing device changed.

[0014] The above-mentioned prior art has several drawbacks.

[0015] In particular, the equipment is so complex that regular inspections are necessary to prevent problems.

[0016] Another drawback is that it is prone to wear.

[0017] Furthermore, the system is so complex that it cannot be miniaturized, which is particularly true for grinding wheels for internal grinding and for grinding wheels for holes in workpieces, since these wheels are too small to support a balancing system.

[0018] These complications and problems are exacerbated by the considerable forces that are exerted during operation, with the rotor reaching speeds equivalent to tens to thousands of revolutions per minute. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] European Patent Application Publication No. 2717032 [Patent Document 2] U.S. Patent No. 17,886,005 [Patent Document 3] European Patent Application Publication No. 19158944 [Patent Document 4] European Patent Application Publication No. 13156332 Summary of the Invention [Problem to be solved by the invention]

[0020] In view of this situation, the technical problem of the present invention is to devise a balancing device that can substantially overcome at least some of the above-mentioned drawbacks.

[0021] Within this technical problem, an important object of the present invention is to obtain a balancing device that is simple and robust.

[0022] A further important object of the present invention is to provide a precision balancing device.

[0023] A further important object of the present invention is to provide a wheel balancing system for holes in workpieces.

[0024] SUMMARY OF THE INVENTION It is an object of the present invention to at least provide an inexpensive balancing device. [Means for solving the problem]

[0025] The technical problem and stated objectives are achieved by a balancing device as set forth in the attached claim 1.

[0026] Preferred technical solutions are highlighted in the dependent claims. [Brief explanation of the drawings]

[0027] The features and advantages of the present invention will become apparent in the following detailed description of preferred embodiments of the invention, which proceeds with reference to the accompanying drawings. [Figure 1] FIG. 1 shows a diagram of a balancing device according to the invention. [Figure 2] FIG. 2 shows a second view of the cross section of the balancing device according to the invention. [Figure 3a] FIG. 3a shows a third example of a balancing device according to the invention in a schematic side view. [Figure 3b] FIG. 3b is a cross section taken along line BB in FIG. 3a. DETAILED DESCRIPTION OF THE INVENTION

[0028] In this specification, measurements, values, shapes, geometric features (e.g., perpendicular or parallel) are described with the words "about" or similar expressions such as "approximately" or "substantially." However, measurement errors or loss of precision due to production and / or manufacturing errors are not taken into consideration, particularly when there is a slight deviation from the value, measurement, shape, or geometric feature accompanied by such an expression. For example, when these expressions are used in conjunction with a value, it is preferable that the deviation from the value is 10% or less.

[0029] Furthermore, when terms such as "first," "second," "higher," "lower," "primary," "secondary," etc. are used, they do not necessarily specify an order, precedence, or relative position, but are simply used to clearly distinguish between different components.

[0030] Unless otherwise specified, in the following descriptions and results, the terms "processing," "operating," "determining," "calculating," and similar terms refer to computer and similar electronic computing machine operations and / or steps that manipulate and / or transform physical data, such as electronic quantities in registers of a computer system and / or memory, in a transmitting device, in an information display device, or other data similarly represented as physical quantities in a computer system, register, or other storage.

[0031] Measurements and data reported in this document were obtained under the International Standard Atmosphere ICAO (ISO 2533:1975) unless otherwise stated.

[0032] With reference to the drawings, a balancing device according to the invention is designated throughout by the reference numeral 1.

[0033] Conveniently, it forms part of a balancing mechanism, as will be described below, and comprises a rotor 10. The rotor 10 preferably comprises the rotor of a machine tool, such as a grinding wheel, or other device, and defines an axis of rotation 10a.

[0034] In an important variant of the invention, the rotor 10 is a tool, in particular an abrasive wheel, for machining, in particular grinding, the internal cavities of the component.

[0035] To reach optimal cutting speeds (over 30 m / s), the wheel must undergo tens or even thousands of revolutions. At these high rotational speeds, even minor imbalances can cause vibrations that affect the machining quality and even the lifespan of the spindle itself. Furthermore, the wheel-holding shafts are often long, making them highly susceptible to wheel imbalances.

[0036] The balancing device 1 comprises a fixed part 2 and a movable part 3. The fixed part 2 is preferably fixed relative to a floor surface, and the movable part 3 is preferably rotatable and defines a central axis 3a.

[0037] The movable part 3 is preferably integrated with the rotor 10 and is controllable, so that the central axis 3a substantially coincides with the rotation axis 10a.

[0038] The balancing device 1 has the purpose of eliminating imbalances in a system comprising the moving part 3 and the rotor 10 of the balancing device 1. Such imbalances are eliminated when the centers of mass of the moving part 3 and the rotor 10 of the system lie along the axis of rotation 10a.

[0039] The movable part 3 preferably includes at least one eccentric mass 30, more preferably two eccentric masses 30 balanced about the central axis 3a, that are rotatable about the central axis 3a. Each eccentric mass 30 is preferably rotatable independently of the other mass and the rest of the movable part 3 about the central axis 3a.

[0040] The eccentric mass 3 consists of two annular elements, for example symmetrically arranged parts, with their axes aligned along a central axis 3a.

[0041] The balancing device 1 also preferably comprises means 4 for moving each eccentric mass 30. The means 4 are mounted integral with the rotor 10 about a central axis 3a so as to rotate each eccentric mass 30 relative to the other eccentric masses 30 and other points on the moving part 3.

[0042] The moving means 4 preferably comprises a magnetic brake 40 .

[0043] As is known, magnetic brakes, which are used in technical fields quite different from the present invention, such as high-speed trains, make use of the eddy current phenomenon.

[0044] Eddy currents are electrical currents induced in a conductor in a changing magnetic field. The fluctuations occur due to the back-and-forth motion between the magnetic field and the conductor. The changing magnetic field causes electrons to circulate within the conductor, according to Faraday's Law. The movement of these electrons, and therefore this current, creates a magnetic field that opposes the back-and-forth motion between the magnetic field and the conductor, and that opposes the direction of the applied magnetic field fluctuations. This opposing force is what causes a magnetic brake to function.

[0045] The magnetic brake 40 preferably comprises at least one conductive part 41 made of a conductive material, and at least one magnetic part 42 capable of forming a magnetic field acting on the conductive part 41 .

[0046] Either one of the conductive portion 41 and the magnetic portion 42, preferably the conductive portion 41, is preferably integrated with the eccentric mass 30, and more preferably the conductive portion 41 coincides with the eccentric mass 30. For example, the eccentric mass is made of a material having high electrical conductivity, such as a metal material containing mainly aluminum or copper.

[0047] In a preferred example, the conductive portion 41 that matches the eccentric mass 30 includes a peripheral portion 41a and a central portion 41b.

[0048] The peripheral portion 41a is the peripheral ring of the eccentric mass 30 and is preferably made of copper, aluminum, or a non-ferromagnetic, highly conductive material. The peripheral portion 41a also preferably has a radial thickness of less than 1 cm, more preferably 5 mm or less, and even more preferably 1 mm to 5 mm. Furthermore, the peripheral portion preferably has a thickness of 0.5% to 5%, and even more preferably 1% to 3% of the diameter of the eccentric mass 30.

[0049] The central portion 41b, preferably adjacent to the peripheral portion 41a toward the inside of the mass 30, has a greater thickness. Preferably, the radial thickness of the central portion 41b is greater than 5 mm, more preferably 5 mm to 2 cm, and even more preferably 8 mm to 15 mm. Furthermore, preferably, the peripheral portion has a thickness of 5% to 20% of the diameter of the eccentric mass 30, and even more preferably 10% to 15%.

[0050] The ratio of the radial lengths of the central portion 41b and the peripheral portion 41a is more preferably 3-50, more preferably 5-25, and even more preferably 6-20.

[0051] Preferably it is made of a ferromagnetic material, more preferably ferromagnetic steel, iron, etc. These materials, shapes and dimensions surprisingly maximize the efficiency of the device 1 and the effectiveness of the magnetic brake.

[0052] Preferably, one of the conductive portion 41 and the magnetic portion 42, more preferably the magnetic portion 42, is fixed with respect to the rotation of the component 50. More preferably, two magnetic portions 42 are provided on each mass, and only one of them is movable in the direction of the central axis 3a.

[0053] In a first preferred example, the magnetic part 42 comprises a permanent magnet 43 , for example neodymium, and means 44 for adjusting the distance between the permanent magnet 43 and the conductive part 41 .

[0054] The adjustment means 44 may define, at least in part, a track extending radially transverse to the central axis 3a. The adjustment means 44 may further comprise an electric motor or the like.

[0055] In a second preferred embodiment, not shown in the drawings, the magnetic portion 42 comprises an electromagnet, preferably having an annular shape or portion and arranged around an eccentric mass.

[0056] In a third example (FIG. 2), the magnetic part 42 includes an electromagnet 42a consisting of at least one coil having an axis radial to the central axis 3a. In this case, an adjustment means 44 may or may not be provided, and more preferably, it is not provided and the electromagnet is fixed. More preferably, two or more coils are provided, preferably two to eight, and even more preferably four. The coils are preferably arranged at regular intervals in the circumferential direction around the axis 3a.

[0057] In a fourth example (FIGS. 3a and 3b), particularly for use in a grinding wheel for internal cavities in components, the magnetic part 42 comprises at least one electromagnet 42a, similar to the electromagnet of the third example, and means 44 for adjusting the distance between the electromagnet and the conductive part 41. In this case, the adjustment means 44 has the purpose of adjusting the electromagnet 42a to move it closer to the eccentric mass or to move it away from the eccentric mass, thereby allowing for a clearance and movement, in particular an axial movement of the eccentric mass. In this example, the final part of the magnetic part 42 preferably has a shape corresponding to the mass 30. Furthermore, a component such as a Hall sensor or a magnet 80, which changes the position of the mass itself, is also provided at this position.

[0058] To allow movement by the magnetic brake 40, the eccentric mass 30 is preferably fixed to other parts of the moving part 3, or directly fixed to the rotor 10 by a rotation bearing 31 with a non-zero coefficient of friction, such as a polymer bearing. The bearing 31 provides sufficient resistance to fix the mass 30 relative to other parts of the moving part 3. This supports the rotational acceleration of the rotor 10, and at the same time, the magnetic brake 40 moves and brakes the eccentric mass 30 relative to other parts of the moving part 3.

[0059] Sensors are preferably provided within the device 1 to sense the angular position of each eccentric mass 30, thereby facilitating balancing.

[0060] The balancing mechanism comprises a balancing device 1, preferably with or without being inserted in the device 1, means for detecting imbalance, such as known accelerometers, a synchronization sensor for detecting the rotation of the shaft 10a, power supply means connected to the electric motor or electromagnet mentioned above, and control means for sending and receiving information and controlling the movement means 4 or other elements. The balancing mechanism may further comprise sensor means suitable for sensing contact between the rotor 10 and the workpiece, in particular when the rotor 10 consists of a tool such as a grinding wheel.

[0061] The balancing device 1 and balancing mechanism described structurally operates as follows.

[0062] A new process is defined to move the eccentric mass 30 around the central axis 3a and correct the mass center of the rotor 10. In this process, the eccentric mass 30 is preferably moved by magnetic braking means, preferably operated by a moving means 4. The moving means 4 preferably comprises a magnetic brake 40, the moving means 4 preferably being of the type described above.

[0063] This process is preferably carried out by the balancing device 1 described above and preferably by the balancing mechanism described above.

[0064] Specifically, the movable part 3 of the balancing device 1 is fixed precisely to the shaft of the rotor 10. As a result, the central axis 3a substantially coincides with the rotation axis 10a.

[0065] First, when the rotor is balanced, the two eccentric masses 30 are offset at an angle of 180 degrees, which causes the balancing device 1 to also be balanced, and the two objects as a whole to be balanced.

[0066] If an imbalance occurs in the rotor 10, the imbalance detection means detects and measures the imbalance and transmits the result to the control means.

[0067] This controls the moving means 4 to strengthen the magnetic field applied to the eccentric mass 30 .

[0068] In particular, the adjustment means 44 moves the permanent magnet 43 closer to the conductive portion 41 of the eccentric mass 30. Alternatively, or in addition to the above, the electromagnet generates a relatively strong magnetic field in the vicinity of the eccentric mass 30.

[0069] Eddy currents generated in the magnetic field created by permanent magnet 43 cause current movement along eccentric mass 30 in opposition to the reciprocating motion between permanent magnet 43 and eccentric mass 30. This reciprocating motion is a rotational motion about axis 10a, and is therefore damped, and the rotational drive about bearing 31 changes the angular position of the movable part 3 relative to other parts.

[0070] The eccentric mass 30 is then rotated until the imbalance of the balancing device 1 is corrected and counterbalanced to the imbalance of the rotor 10, thereby achieving balance.

[0071] When the magnetic field is weakened, for example by moving the permanent magnet 43 away from the eccentric mass 30 or by weakening the field of the electromagnet, the strength of the eddy currents decreases, which in turn reduces the strength of the magnetic field, and the eccentric mass 30 reintegrates with the rest of the moving part 3 and the rotor 10.

[0072] The balancing device 1 according to the invention offers important advantages.

[0073] In fact, the balancing device is simple and robust and does not require complex rotary motors, etc. Therefore, the device can be mounted on a plate rotating element that rotates at speeds exceeding tens to thousands of rpm.

[0074] For the same reason, the device is very economical.

[0075] Furthermore, in situations where significant miniaturization is required, the balancing device 1 according to the invention is applicable to tools, in particular grinding wheels for machining, in particular grinding, internal cavities of parts.

[0076] The present invention includes modifications that do not depart from the scope of the inventive concept defined in the claims, i.e., all elements may be arbitrarily substituted with equivalent elements, materials, shapes and dimensions.

Claims

1. A balancing device (1) for a rotor (10), comprising: The rotor (10) defines an axis of rotation (10a); The balancing device (1) A fixed part (2), A movable part (3) defining a central axis (3a), The movable part (3) is constrained to the rotor (10) so that the central axis (3a) substantially coincides with the rotation axis (10a), the movable part (3) comprising at least one eccentric mass (30) rotatable about the central axis (3a) and unbalanced with respect to the central axis (3a); A means (4) for moving at least one of the eccentric masses (30), said moving means (4) suitable for rotating said eccentric mass (30) about said central axis (3a) relative to said rotor (10); and The moving means (4) comprises a magnetic brake (40), and The eccentric mass (30) comprises a peripheral portion (41a) made of a non-ferromagnetic material having high electrical conductivity and a central portion (41b) made of a ferromagnetic material. A balancing device (1) characterized in that:

2. The magnetic brake (40) comprises at least a conductive part (41) made of a conductive material and at least one magnetic part (42) suitable for generating a magnetic field acting on the eccentric mass (30). Balancing device (1) according to claim 1, characterized in that:

3. The conductive portion (41) is integrated with the eccentric mass (30), and the magnetic portion (42) is fixed against rotation around the rotation axis (10a). Balancing device (1) according to claim 2, characterized in that:

4. The conductive portion (41) is aligned with the eccentric mass (30). Balancing device (1) according to claim 3, characterized in that:

5. The magnetic portion (42) includes at least one electromagnet (42a). Balancing device (1) according to any one of claims 2 to 4, characterized in that it

6. The electromagnet (42a) has an axis radially relative to the central axis (3a). Balancing device (1) according to claim 5, characterized in that

7. A plurality of the electromagnets (42a) are fixed in the radial direction. Balancing device (1) according to claim 6, characterized in that

8. The magnetic portion (42) includes a means (44) for adjusting the distance between the electromagnet (42a) and the conductive portion (41). Balancing device (1) according to claim 5 or 6, characterized in that

9. said adjusting means (44) comprising an electric motor; Balancing device (1) according to claim 8, characterized in that

10. The peripheral portion (41a) has a thickness corresponding to 0.5% to 5% of the diameter of the eccentric mass (3). Balancing device (1) according to any one of claims 1 to 9, characterized in that it

11. The ratio of the length of the central portion (41b) to the length of the peripheral portion (41a) in the radial direction is 3 to 50. Balancing device (1) according to any one of claims 1 to 10, characterized in that it

12. Equipped with a balancing device (1) according to any one of claims 1 to 11, A machine tool characterized by:

13. It consists of a machine tool that processes the internal holes of the parts. Machine tool (1) according to claim 12, characterized in that

14. Machine tool (1) according to claim 13, characterized in that it consists of a grinding wheel.

15. A method for correcting the mass center of a rotor (10) by moving an eccentric mass (30) around a central axis (3a), comprising: The eccentric mass (30) is moved by magnetic braking. A method characterized by:

Images