Magnetic Gears — Clean, Quiet, and Safe Motion Powered by Non-Contact Technology
- No particle generation from tooth surface wear
- Operates without the need for Lubrication
- Barrier transmission allows for seal-less designs
- Low noise and vibration due to non-contact power transmission
- Easier assembly with high angular and eccentric misalignment tolerance
- Magnetic slip under overload enhances safety conditions
- Vibration Transmission Reduction
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What Are Magnetic Gears?
A magnetic gear (non-contact gear) is a toothless power transmission component that uses the magnetic force generated by permanent magnets such as neodymium magnets to transmit rotational speed and torque between two shafts without physical contact. Because power is transmitted without contact, magnetic gears offer unique advantages over conventional mechanical gears.
Learn more in the “Principle of Magnetic Gears” section below
Left: Conventional spiral bevel gears
Center: Magnetic bevel gears
Right: Magnetic pole configuration
Potential Applications by Industry
- Semiconductor Manufacturing Equipment Industry
- Robotics Industry
- Medical Device Industry
- Food Processing Machinery Industry
Magnetic Gear Product Lineup
A combination of a disc and a cylindrical element, equivalent to bevel gears in conventional gearing, used to transmit torque and rotational speed between perpendicular shafts.
A combination of cylindrical elements, equivalent to screw gears in conventional gearing, used to transmit torque and rotational speed between skew shafts.
A cost-effective version of Magnetic Screw Gears. The magnet portions are epoxy-coated, while the yoke has no surface treatment.
Magnetic gears equivalent to conventional spur gears, used to transmit torque and speed between two parallel shafts.
Non-contact magnetic variable-speed gears offering a high degree of design flexibility in gear ratios.
A cylindrical-type non-contact magnetic transmission gear capable of both speed increase and reduction.
Non-contact linear actuators using magnetic force. Ideal for transport applications in cleanroom environments. They require no wiring like conventional linear motors and can be extended to virtually unlimited lengths.
A non-contact version of conventional rack and pinion systems, using magnetic force to convert rotational motion into linear motion.
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Key Features of Magnetic Gears
No particle generation caused by tooth surface wear :
In conventional gears, direct contact between tooth surfaces inevitably generates minute wear particles. Insufficient lubrication can further accelerate wear, leading to increased particle generation. In applications requiring high cleanliness, such as semiconductor manufacturing equipment, contamination from these particles may adversely affect equipment performance and product quality. In contrast, magnetic gears transmit power without tooth contact, fundamentally eliminating particle generation caused by tooth surface wear. This makes them particularly suitable for cleanroom and other contamination-sensitive applications.
Lubrication-free operation :
Conventional gears transmit power through direct contact between tooth surfaces, making lubrication essential in many applications. Users must select appropriate lubrication methods and lubricants, while also managing oil starvation and periodic replacement, which can increase maintenance effort and operating costs. In cleanroom and vacuum environments, additional concerns such as lubricant splashing, evaporation, oil mist generation, grease outgassing, and particle adhesion must also be considered. In contrast, magnetic gears transmit power through magnetic force without physical contact, eliminating the need for tooth surface lubrication. This helps reduce maintenance requirements, minimize equipment downtime, and support cleaner operating environments.
Barrier transmission enables seal-less structures :
Magnetic gears transmit torque without physical contact between the driving and driven rotors. As a result, power can be transmitted through a non-magnetic barrier such as resin or stainless steel, eliminating the need for shaft penetrations or conventional sealing mechanisms. This enables seal-less structures in applications such as food processing equipment, where a motor outside a sealed chamber can drive an internal mixing component without contact, helping reduce contamination risks and improve cleanability. Power can also be transmitted into liquid-filled containers without through-holes, reducing leakage risks and simplifying system design. The transmitted torque depends on factors such as the magnet gap and the material and thickness of the barrier, which should be considered during the design process.
Low noise and vibration through non-contact power transmission :
In mechanical design, reducing vibration and noise in drive systems is an important challenge that directly affects product performance and added value. Conventional gears transmit power through physical tooth engagement, and therefore some vibration and noise may occur due to factors such as meshing impacts, machining accuracy, assembly errors, and lubrication conditions. In contrast, magnetic gears transmit power through magnetic interaction without physical tooth contact. As a result, vibration and noise caused by tooth collision and friction do not occur, enabling quieter and smoother operation compared with conventional mechanical gears. This characteristic makes magnetic gears an effective option for applications where low noise, low vibration, and stable operation are important requirements.
Easier assembly with high angular and eccentric misalignment tolerance :
Conventional mechanical gears require high assembly accuracy because power is transmitted through direct tooth contact. Precise control of center distance, backlash, and tooth contact is essential, and insufficient accuracy can result in abnormal wear, tooth damage, increased noise, and vibration. In contrast, magnetic gears transmit torque without physical contact and tolerate a certain degree of center distance variation, angular misalignment, and positional offset, making assembly and maintenance easier. However, if the air gap between magnetic poles becomes too large, the transmissible torque decreases and loss of synchronization (slip) may occur.
Magnetic slip under overload helps improve safety :
Magnetic gears feature a built-in torque limiting function enabled by non-contact power transmission through permanent magnets. Under normal conditions, torque is transmitted synchronously between the input and output shafts. However, when the load exceeds the allowable transmissible torque, magnetic slip occurs, preventing excessive torque transmission.
This helps protect motors and surrounding equipment from overload conditions such as sudden stoppages or foreign object intrusion. Because there is no tooth contact, tooth surface damage and wear particle generation are also avoided. In addition, no separate mechanical torque limiter is required, helping simplify system design.
Vibration Transmission Reduction :
With conventional gears and couplings, the input and output sides are physically connected, so vibrations generated on the input side are directly transmitted to the output side. In contrast, magnetic gears (couplings) operate without physical contact, with an air gap between the input and output sides. As a result, vibrations from the input side are less likely to be transmitted directly to the output side, reducing vibration transmission.
However, if the input and output sides are mechanically connected through another path, such as a common base or housing, vibrations may still be transmitted through that path.
Long-Lasting Magnetic Performance :
Magnets are often thought to lose their magnetic strength over time; however, the demagnetization of the magnets used in our magnetic gears is extremely small. According to our data, the maximum rate of demagnetization is only 0.1% per year, resulting in a magnetic strength reduction of only about 1% even after 10 years.
As a result, the effect on transmitted torque is negligible, allowing stable power transmission over long periods of operation. In addition, the need for replacement or adjustment due to performance degradation is minimized, helping to reduce maintenance requirements and lower the total cost of ownership (TCO).
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Principle of Magnetic Gears
Magnetic gears differ from conventional mechanical gears in that they transmit power without physical contact between the teeth. Instead, they utilize the magnetic force generated by permanent magnets, such as neodymium magnets, to transmit power.The following sections explain the basic operating principles of magnetic gears while introducing the key technical terms needed to understand how they work.
1. Torque Transmission Mechanism
For simplicity, the following explanation uses a simplified model of a magnetic gear.
A magnetic gear consists of a pair of rotors with alternating north (N) and south (S) magnetic poles arranged around their circumference. These magnetic poles interact with each other across an air gap, generating attractive forces between opposite poles and repulsive forces between like poles. As the input rotor rotates, these magnetic forces transmit torque to the output rotor, allowing both rotors to rotate synchronously without any physical contact.
2. Relationship Between Speed Ratio and Torque
As with conventional mechanical gears, magnetic gears follow the same fundamental relationship between speed ratio and torque.
The speed ratio is determined by the ratio of the number of magnetic poles on each rotor, and the output torque varies accordingly.
Torque Increase and Speed Reduction
When power is transmitted from a rotor with fewer magnetic poles to one with more magnetic poles, the rotational speed decreases while the output torque increases.Torque Decrease and Speed Increase
When power is transmitted from a rotor with more magnetic poles to one with fewer magnetic poles, the rotational speed increases while the output torque decreases.
Thus, as with conventional mechanical gears, rotational speed and torque are generally in an inverse relationship. However, in practical systems, losses such as mechanical and magnetic losses may occur, so the actual change in torque may not exactly match the theoretical value.
3. Air Gap
In magnetic gears, the transmissible torque depends on the size of the air gap (the distance between the rotors). As the air gap increases, the magnetic flux density within the air gap decreases, weakening the magnetic interaction (attractive and repulsive forces) between the rotors. As a result, the transmissible torque also decreases.
Therefore, when using magnetic gears, it is important to ensure an appropriate air gap by considering factors such as the available installation space and the required transmissible torque.
4. Lost Motion
What Is Lost Motion?
In magnetic gears, Lost Motion is the phase difference (rotational displacement) between the input and output sides. During torque transmission, this phase difference develops in response to the applied load torque. The resulting magnetic restoring force (which acts to return the phase difference to zero) is what enables the magnetic gear to transmit torque.
Zero Phase Difference
Please refer to Figure 1.
For simplicity, the following explanation uses a simplified coupling-type 8-pole model to illustrate the basic principle of Lost Motion in magnetic gears. In the stationary state (zero torque), the input-side S pole and the output-side N pole, highlighted by the red circles, are directly aligned with each other, resulting in a phase difference of 0°.
At first glance, it may seem that this 0° phase difference represents the strongest magnetic coupling and therefore the maximum torque transmission. In reality, however, this is not the case.
As explained above, magnetic gears transmit torque by generating a phase difference between the input and output sides under load. This phase difference creates the magnetic restoring force required for torque transmission.
In other words, when the phase difference is 0°, no magnetic restoring force is generated, and therefore no torque is transmitted.
Relationship Between Phase Difference and Transmitted Torque
Please refer to Figure 2.
For simplicity, the magnetic pole geometry and magnetic flux distribution have been simplified in this illustration.
In this 8-pole model, one pole pitch corresponds to 45° (360° ÷ 8).
As the load torque increases, the phase difference gradually increases from 0°. The input-side magnetic pole (the S pole highlighted by the red circle) gradually moves away from the opposite output-side N pole, while simultaneously approaching the adjacent output-side S pole.
As a result, the attractive force between opposite poles and the repulsive force between like poles act simultaneously. The combination of these forces produces a rotational torque that acts to reduce the phase difference—that is, the magnetic restoring force.
In this simplified 8-pole model, when the phase difference reaches approximately 22.5°, which is half of one pole pitch (45°), the combined rotational effect of the attractive and repulsive forces becomes greatest, producing the maximum magnetic restoring force.
Consequently, the maximum transmissible torque is achieved at approximately 22.5°.
If the load torque increases further, the magnetic coupling can no longer be maintained, causing synchronization between the input and output sides to be lost, resulting in pole slip (loss of synchronism).
Points to Consider Regarding Lost Motion
During actual operation, the phase difference continuously changes in response to variations in load torque. As a result, a certain amount of phase difference may always exist between the input and output sides of a magnetic gear. For applications requiring high positioning accuracy or precise synchronization, the effects of Lost Motion should be carefully considered.
Summary
- Lost Motion is the phase difference (rotational displacement) between the input and output sides.
- Magnetic gears transmit torque by utilizing the magnetic restoring force generated by this phase difference.
- As the load torque increases, both the phase difference and the corresponding magnetic restoring force increase.
- In the simplified 8-pole model presented here, the maximum transmissible torque is reached at a phase difference of approximately 22.5°.
- If the load torque exceeds the maximum transmissible torque, pole slip (loss of synchronism) occurs.
- For applications requiring high positioning accuracy, the effects of Lost Motion should be taken into account.
- Unlike backlash in conventional mechanical gears, Lost Motion is an essential operating characteristic that enables magnetic gears to transmit torque.
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Potential Applications of Magnetic Gears by Industry
Cleanroom Conveying System
Semiconductor Manufacturing Equipment Industry
1. Particle Generation and Contamination Control
Potential Challenge:
In semiconductor manufacturing, microscopic particles such as wear debris from gears and bearings, as well as lubricant mist, can reduce production yield.
Solution:
Magnetic gears transmit torque without physical contact, eliminating wear particles from contact surfaces and the need for lubrication. They provide clean power transmission and help improve production yield by reducing particle generation.
2. Reduced Maintenance and Downtime
Potential Challenge:
Periodic lubrication, replacement of worn components, and maintenance of shaft seals result in equipment downtime and reduced productivity.
Solution:
Because torque is transmitted without physical contact, wear is minimal and no lubrication is required. This reduces the frequency of component replacement and maintenance, helping improve equipment uptime while lowering total cost of ownership (TCO).
3. Support for Vacuum and Sealed Processes
Potential Challenge:
In vacuum chambers and special gas environments, leakage through rotary shaft seals and outgassing can become issues.
Solution:
Magnetic couplings can transmit torque across a barrier without physical contact, eliminating the need for a rotating shaft to penetrate the barrier. This helps maintain a high level of airtightness and improves the reliability of vacuum equipment and sealed processes.
The feasibility of non-contact torque transmission and the transmissible torque depend on factors such as the material and thickness of the barrier.
Robotics Industry
1. Wear and Maintenance
Potential Challenge:
Continuous operation of robots can lead to wear of drive components, requiring lubrication management, component replacement, and other maintenance work.
Solution:
Since power is transmitted non-contact through magnetic force, wear caused by mechanical contact, such as between gear teeth, can be reduced. In addition, no lubrication is required, helping reduce maintenance requirements and enabling cleaner drive mechanisms.
2. Damage Caused by Collisions and Overloads
Potential Challenge:
If a robot collides with a workpiece or surrounding equipment, or is subjected to an unexpected overload, drive components such as motors, reducers, and gears may be damaged.
Solution:
When the maximum transmissible torque is exceeded, the magnetic poles can slip relative to each other without mechanical contact. This helps limit excessive torque from being transmitted to surrounding drive components, reducing the risk of damage.
3. Vibration and Noise
Potential Challenge:
Vibration and noise generated by motors and drive mechanisms can be transmitted to the robot itself and surrounding equipment, affecting quiet operation and equipment performance.
Solution:
Since the input and output sides are not physically connected, direct vibration transmission from the input side to the output side can be reduced compared with mechanically connected gears and couplings. In addition, because there is no mechanical meshing between gear teeth, noise caused by mechanical contact can also be reduced.
Medical Device Industry
1. Reduced Maintenance and Downtime
Potential Challenge:
Medical devices may require lubrication, periodic replacement of worn components, and maintenance of shaft seals, which can result in increased equipment downtime and higher maintenance costs.
Solution:
Magnetic gears transmit torque without physical contact, resulting in minimal wear and eliminating the need for lubrication. This can help reduce the maintenance workload, improve equipment uptime, and lower the total cost of ownership (TCO).
2. Improved Cleanliness and Hygiene
Potential Challenge:
Medical devices require a high level of hygiene. Lubricant leakage and the generation of wear particles may increase the risk of contamination and add to the burden of cleaning and sterilization.
Solution:
Because magnetic gears transmit power without physical contact, they generate no wear particles and require no lubrication. As a result, they provide clean power transmission and are expected to contribute to improved hygiene and cleaner operation of medical devices.
3. Quieter and Lower-Vibration Operation for a More Comfortable Medical Environment
Potential Challenge:
In hospital rooms, examination rooms, and consultation rooms, noise and vibration from medical equipment may affect patient comfort and the working environment for healthcare professionals.
Solution:
Because magnetic gears operate without tooth-to-tooth contact, they provide quieter, lower-vibration operation than conventional mechanical power transmission systems. They are expected to contribute to a more comfortable medical environment while also supporting the stable operation of precision equipment.
Food Processing Machinery Industry
1. Reducing the Risk of Product Contamination
Potential Challenge:
In food processing, lubricant leakage and wear particles generated by mechanical components can become sources of product contamination, potentially leading to reduced product quality and product recalls.
Solution:
Magnetic gears transmit torque without physical contact, resulting in virtually no wear particle generation in the torque transmission section while requiring no lubrication. This helps reduce the risk of contamination caused by wear particles and lubricants, contributing to a cleaner food processing environment.
2. Reducing Cleaning and Maintenance Workload and Minimizing Downtime
Potential Challenge:
Food processing equipment requires frequent cleaning to maintain a high level of hygiene, which can increase equipment downtime. In addition, equipment shutdowns caused by component wear, lubrication, and periodic replacement can reduce productivity and increase maintenance costs.
Solution:
Magnetic couplings can transmit torque through a barrier, making it possible to achieve a completely sealed product-side structure. In addition, because magnetic gears and magnetic couplings transmit torque without physical contact, they experience minimal wear and require no lubrication. This helps improve cleanability and hygiene while reducing maintenance workload, increasing equipment uptime, and lowering the total cost of ownership (TCO).
3. Reducing the Risk of Equipment Damage Caused by Overload
Potential Challenge:
In food processing equipment, products or foreign objects may become jammed, or sudden load fluctuations may occur, resulting in excessive loads being applied to drive components such as gears and motors. As a result, components may be damaged, equipment may stop unexpectedly, and repair costs may increase.
Solution:
When the applied load exceeds the maximum transmissible torque, magnetic gears can slip magnetically, limiting the transmission of excessive torque. This helps reduce the risk of damage to drive system components, protecting equipment and preventing unexpected downtime.
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