Magnetic bearings are a type of support system that uses magnetic forces to suspend or bear the load of a rotor. Over the years, this technology has developed rapidly and is now widely used in high-speed, low-friction, high (or low) temperature, and vacuum environments. Compared to traditional mechanical bearings, magnetic bearings offer several advantages, such as high precision, safe operation, and reliability. They also have great potential for future applications.
### Key Features and Classification
1. **Key Characteristics**
- No physical contact between moving parts, which reduces wear and tear.
- High accuracy and stability during operation.
- Capable of functioning in extreme environments, such as high temperatures, deep cold, and vacuum conditions.
- Require careful design due to complex electromagnetic interactions and possible magnetic interference with surrounding equipment. However, they do not produce pollution like oil or dust.
2. **Classification**
Magnetic bearings can be classified based on control methods, magnetic field types, and structural layouts. Common classifications include:
- **Permanent Magnet Bearings**: These are passive systems that rely on permanent magnets. However, they cannot maintain stability in all three directions without an active component.
- **Electromagnetic Bearings**: These require external power and are usually active, offering more control over the bearing's behavior.
- **Hybrid Bearings**: Combine permanent magnets and electromagnets for enhanced performance.
- **Suction vs. Repulsion Bearings**: Suction-type bearings use attraction, while repulsion-type bearings use magnetic repulsion. The latter often requires more space and is less commonly used due to lower efficiency.
### Typical Applications
Although still under development, magnetic bearings are being tested in various specialized fields:
1. **Machine Tools**
- In France, S2M company developed a high-precision spindle with 5 degrees of freedom using magnetic bearings. It achieves a radial dn value of 4×10ⶠmm·rpm and a rotational speed of 200 m/s.
- Another super-precision lathe uses automatic magnetic bearings, achieving 2000 rpm with a power consumption of 1 kW and a processing accuracy of 0.05 µm.
2. **Fine Instruments**
- The UK’s National Physical Laboratory developed a magnetic levitation guide rail for high-resolution measurement. It offers a stiffness of 175 N/mm and a resolution of 0.11 nm in the 1 kHz frequency range.
3. **Pumps**
- A blood pump developed by the University of Tokyo and NTN uses a 5-degree-of-freedom magnetic bearing, with radial and thrust capacities of 18N, 22N, and 9.2N respectively.
- France’s SEP company uses magnetic bearings in liquid oxygen and hydrogen pumps for rocket engines.
4. **Space Technology**
- Japanese companies like NAL & MELCO and NAL & TOSIBA use magnetic bearings to support inertia wheels for spacecraft attitude control.
5. **Physics Experiments**
- Germany’s Uranit introduced three particle beam converters using magnetic bearings.
- KFA Germany developed a neutron selector with a single-degree-of-freedom magnetic bearing, rotating at 36,000 rpm.
### Conclusion
Magnetic bearings represent a significant advancement in bearing technology, offering numerous benefits in terms of performance, longevity, and adaptability. While still in experimental stages and not yet mass-produced, their potential in high-tech industries continues to grow. As research progresses, we can expect broader commercial applications in the near future.
For more information on bearings and their applications, visit China Bearing Network.