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Magnetic gear

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drawings of patent US687292

A magnetic gear resembles the traditional mechanical gear in geometry and function. Near proximity of a plurality of magnet sets enable torque transfer. As opposed to conventional hard contact backlash, the magnetic gear has a springy backlash. Although they provide a motion ratio as a traditional gear, such gears work without touching and so are immune to wear of mating surfaces, have no noise, and may slip without damage.

A magnetically coupled gear can be used in vacuum without lubrication. They can be used in configurations such as operations involving hermetically sealed barriers. This can be an advantage in explosive or otherwise hazardous environments where leaks constitute a real danger.


Design

Magnetic gear systems typically use permanent magnets. They may also use electromagnets for specialized cases including changeable gear ratio.

Magnetic gear coupling concepts may include these configurations

Parallel input and output axes, similar to mechanical gears

Magnetic attraction between cogs, such as north pole attracting south pole of driven element

Repulsion between cogs. Example north pole cogs tending to center between north pole cogs of driven element. The cogs may be inter meshed to improve coupling.

In-line axes

"flux coupling" A stationary intermediate ferromagnetic cylinder allows a motion ratio due to harmonic relationship between the number of poles input compared to output. There is no equivalent mechanical gear system.

"cycloidal drive" Geometry and gear ratio similar to planetary drives. Identification as "epicyclic" and "eccentric" may also be used.

Magnetic attraction between cogs

Magnetic repulsion between cogs


Magnetic gears advantages:

  1. Leak proof mechanical coupling
  2. Shear / overload proof mechanical coupling
  3. Wear is limited to bearings, not mating contact surfaces of gears
  4. Interchangeable ratios either electronically or mechanically in minutes not hours.

The magnetic gear is a magnetic coupling device that renders a mechanical ratio between two magnetically-coupled devices such that:

  1. They have a ratio of rotation or translational movement between input and output which may be unity in the case of a pure magnetic coupling or one of many gear ratios in a magnetic gearbox.
  2. They have a torque or traction limiting factor based on the magnetic coupling force.
  3. They have no physical contact between the main driving and driven elements.

A magnetic gear is composed of magnets of the type permanent, electromagnetic or otherwise magnetically induced fields. It consists of two or more elements that are usually rotating but can be linear or curve linear in nature.

The classical gear is defined as a ratio of pole pairs. Where the Pole pairs are magnets N-S and S-N in nature. For the ratio to be affected there must be at least two elements. with Magnetic pole pair pieces.

Such devices were invented Armstrong, C. G., 1901, “Power Transmitting Device”, U.S. Pat. No. 0,687,292[1] and developed further from the 1940s[2][3]

Gearing modes

There are four basic magnetic gearing modes.

First-order device

A defined ratio of magnets on one driving element and one driven element. This mode One device such as patented by Andrew French of MGT Australia near Port Stephens NSW and Hungarian Arpad Kasler with his Magnemot can be implemented at angles, and through walls. MGT devices are claimed to be 99.9% efficient which translated to near zero maintenance and roughly a 22% reduction in power losses.

Second-order device

Generally a rotational device. A ratio of magnetic pole pairs, where the least number rotates at a higher rate than the higher number pole pair. An intermediate ferromagnetic pole "stator" is usually held stationary and used to effect the concentration of the magnetic lines of force between the high speed rotor and the low speed rotor. The ratio of High speed to Low Speed is the number of magnetic pole pairs on the high speed rotor to the number of magnetic pole pairs on the low speed rotor. This implies an even number of magnets on both rotors. The Ferromagnetic stator has two alternative solutions. The first being the sum of the number of pole pairs of the two rotors, giving the opposite direction of rotation, and the second having pole pieces numbering the difference between the pole pairs of the rotors, which results in the direction of rotation being the same.

Low Speed Magnets Low Speed Pairs High Speed Magnets High Speed Pairs Iron Stator Pieces Gear Ratio Direction
20 10 14 7 17 10:7 Opposite to input
20 10 14 7 3 10:7 Same as input

Third-order device

Generally a rotational device, where a mode 2 device is modified to have external field coil(s), thus effecting a variable transmission or variable ratio magnetic gear. This type of gear consumes approximately 25% of its input power in the process. This renders the variable magnetic gearbox to less than 75% efficiency. However the lower maintenance and the torque limiting characteristics may find suitability in some applications.

Fourth-order device

The mode 4 device is a modification to the Mode 3 device having a low torque variable speed input, a high torque mechanical input, and a high torque mechanical output. As with the mode 3 device, it consumes approximately 25% of the energy to supply the variable input, however if the variable input is held stationary the device functions as a mode 2 device. Such a device can be termed a torque multiplier.

References

  1. ^ https://www.google.com/patents/US687292
  2. ^ https://www.google.com/patents/US3382386
  3. ^ https://www.google.com/patents/US7438035
  • Krasil'nikov, A. Ya. Krasil'nikov, A. A., 2008, “Calculation of the Shear Force of Highly Coercive Permanent Magnets in Magnetic Systems With Consideration of Affiliation to a Certain Group Based on Residual Induction”, Chemical and Petroleum Engineering, Vol. 44, Nos. 7-8, p. 362-65
  • Furlani, E. P., 2001, “Permanent Magnet and Electromechanical Devices”, Academic Press, San Diego.
  • Lorimer, W., Hartman, A., 1997, “Magnetization Pattern for Increased Coupling in Magnetic Clutches”, IEEE Transactions on Magnetics, Vol. 33, No. 5, September 1997
  • Armstrong, C. G., 1901, “Power Transmitting Device”, U.S. Pat. No. 0,687,292
  • Neuland, A. H., 1916, “Apparatus for Transmitting Power”, U.S. Pat. No. 1,171,351
  • Faus, H. T., 1940, “Magnet Gearing”, U.S. Pat. No. 2,243,555
  • Reese, G. A., 1967, “Magnetic Gearing Arrangement”, U.S. Pat. No. 3,301,091
  • Schlaeppi, H. P., 1968, “Magnetic Gears”, U.S. Pat. No. 3,382,386
  • Liang, N., 1972, “Magnetic Transmission”, U.S. Pat. No. 3,645,650
  • Mabe, Jr., W. J., 1991, “Magnetic Transmission”, U.S. Pat. No. 5,013,949
  • Storaasli, A.G., 2016, "Eccentric Magnetic Gear System Based On Repulsion", U.S. Pat. No 9,337,712
  • Ackermann, B., Honds, L., 1997, “Magnetic drive arrangement comprising a plurality of magnetically cooperating parts which are movable relative to one another”, U.S. Pat. No. 5,633,555
  • Yao, Y., Lee, C., Wang, S., Huang, D., 2000, “Method of designing optimal bi-axial magnetic gears and system of the same”, U.S. Pat. No. 6,047,456
  • Furlani, E. P., 2000, “Analytical analysis of magnetically coupled multipole cylinders”, J. Phys. D: Appl. Phys., Vol. 33, No. 1, p. 28-33.
  • Jorgensen, F. T., Andersen, T. O., Rasmussen P. O., 2005, “Two dimensional model of a permanent magnet spur gear”, Conf. Record of the 2005 IEEE Industry Applications Conference, p. 261-5
  • Krasil'nikov, A. Ya. Krasil'nikov, A. A., 2009, “Torque Determination for a Cylindrical Magnetic Clutch”, Russian Engineering Research, Vol. 29, No. 6, pp. 544–47
  • Kyung-Ho Ha, Young-Jin Oh, Jung-Pyo Hong, 2002, “Design and Characteristic Analysis of Non-Contact Magnet Gear for Conveyor by Using Permanent Magnet”, Conf. Record of the 2002 IEEE Industry Applications Conference, p. 1922–27
  • General Electric DP 2.7 Wind Turbine Gearbox, http://www.gedrivetrain.com/insideDP27.cfm, referenced June 2010
  • Neugart PLE-160, One-Stage Planetary Gearbox, http://www.neugartusa.com/ple—160_gb.pdf, referenced June 2010
  • Boston Gear 221S-4, One-stage Helical Gearbox, http://www.bostongear.com/pdf/product_sections/200_series_helical.pdf, referenced June 2010
  • Atallah, K., Howe, D. 2001, “A Novel High-Performance Magnetic Gear”, IEEE Transactions On Magnetics, Vol. 37, No. 4, July 2001, p. 2844–46
  • Charpentier, J. F., Lemarquand, G., 2001, “Mechanical Behavior of Axially Magnetized Permanent-Magnet Gears”, IEEE Transactions on Magnetics, Vol. 37, No. 3, May 2001, p. 1110–17
  • Xinhua Liu, K. T. Chau, J. Z. Jiang, Chuang Yu, 2009, “Design and Analysis of Interior-magnet Outer-rotor Concentric Magnetic Gears”, Journal of Applied Physics, Vol. 105
  • Mezani, S., Atallah, K., Howe, D., 2006, “A high-performance axial-field magnetic gear”, Journal of Applied Physics Vol. 99
  • Cheng-Chi Huang, Mi-Ching Tsai, Dorrell, D. G., Bor-Jeng Lin, 2008, “Development of a Magnetic Planetary Gearbox”, IEEE Transactions on Magnetics, Vol. 44, No. 3, p. 403-12
  • Jorgensen, F. T., Andersen, T. O., Rasmussen, P. O. “The Cycloid Permanent Magnetic Gear”, IEEE Transactions on Industry Applications, Vol. 44, No. 6, November/December 2008, p. 1659–65
  • Atallah, K., Calverley, S. D., D. Howe, 2004, “Design, analysis and realisation of a high-performance magnetic gear”, IEE Proc.-Electr. Power Appl., Vol. 151, No. 2, March 2004
  • Jian, L., Chau, K. T., 2010, “A Coaxial Magnetic Gear With Halbach Permanent-Magnet Arrays”, IEEE Transactions on Energy Conversion, Vol. 25, No. 2, June 2010, p. 319-28
  • Linni Jian, K. T. Chau, Yu Gong, J. Z. Jiang, Chuang Yu, Wenlong Li, 2009, “Comparison of Coaxial Magnetic Gears With Different Topologies”, IEEE Transactions on Magnetics, Vol. 45, No. 10, October 2009, p. 4526-29
  • Correlated Magnetics Research, 2010, Company Website, http://www.correlatedmagnetics.com
  • Jae Seok Choi, Jeonghoon Yoo, Shinji Nishiwaki, and Kazuhiro Izui, 2010, “Optimization of Magnetization Directions in a 3-D Magnetic Structure”, IEEE Transactions on Magnetics, Vol. 46, No. 6, June 2010, p. 1603–06
  • K. T. Chau, Dong Zhang, J. Z. Jiang, Linni Jian, 2008, “Transient Analysis of Coaxial Magnetic Gears Using Finite Element Comodeling”, Journal of Applied Physics, Vol. 103
  • Furlani, E. P., 1996, “Analysis and optimization of synchronous magnetic couplings”, J. Appl. Phys., Vol. 79, No. 8, p. 4692
  • Bassani, R., 2007, “Dynamic Stability of Passive Magnetic Bearings”, Nonlinear Dynamics, V. 50, p. 161-68
  • Tsurumoto, K., 1992, “Basic Analysis on Transmitted Force of Magnetic Gear Using Permanent Magnet”, IEEE Translation Journal on Magnetics in Japan, Vol 7, No. 6, June 1992, p. 447-52
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