Magnetic Couplings

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Non-Contact Magnetic Couplings Enable Clean, Quiet, and Safe Power Transmission

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Potential Applications by Industry

What Is a Magnetic Coupling? – How It Works

See also our FAQ

A coupling is a mechanical component used to connect two shafts and transmit power or rotational motion.
In a conventional coupling (shown in the lower-left illustration), the input and output shafts are mechanically connected to transmit power from one shaft to the other.
In contrast, a magnetic coupling (shown in the lower-right illustration) uses the magnetic force of permanent magnets to transmit torque between the input and output shafts without physical contact.
Attractive and repulsive forces act between the magnets on the input and output sides. When the input shaft rotates, these magnetic forces cause the magnets on the output side to follow, transmitting torque to the output shaft. In general, magnetic couplings operate at a 1:1 speed ratio, with the input and output shafts rotating synchronously at the same speed.
This non-contact power transmission is what gives magnetic couplings their unique characteristics. With no contacting surfaces, there is no wear or particle generation, and no lubrication is required. Non-contact transmission also contributes to low-noise, low-vibration operation and helps reduce the transfer of vibration and heat from the input side to the output side. In addition, power can be transmitted through a barrier placed between the input and output sides, allowing the two sides to be completely isolated from each other. Magnetic couplings also tolerate a certain degree of misalignment, and their non-contact design makes assembly easier.
When the transmitted torque exceeds the allowable limit of the magnetic coupling, magnetic synchronization between the input and output sides is lost, causing the coupling to slip. This prevents excessive torque from being transmitted directly to the output side and provides a built-in torque-limiting function that helps protect motors and machinery from overload conditions.
With these unique advantages of non-contact power transmission, magnetic couplings provide new possibilities for mechanisms and operating environments where conventional couplings may be difficult to use.

Magnetic Coupling Products

Standard Item

Made-to-Order Item

The above product data are values measured under ambient temperature conditions.

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Other Magnetic Coupling Products

Key Features of Magnetic Couplings

No particle generation caused by tooth surface wear

Barrier transmission enables seal-less structures

Low Noise and Vibration Through Non-Contact Power Transmission

Easier assembly with high angular and eccentric misalignment tolerance

Torque Limiting Function Under Overload Conditions

Vibration Transmission Reduction

Reduced Heat Transfer from the Input Shaft

Long-Lasting Magnetic Performance

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Principle of Magnetic Couplings

Magnetic couplings differ from conventional couplings in that they transmit power without physical contact between the input and output sides. 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 couplings while introducing the key technical terms needed to understand how they work.

2. Synchronous Rotation

Magnetic couplings normally use the same number of magnetic poles on both the input and output rotors. As a result, the input and output rotors rotate synchronously at a 1:1 speed ratio.
When torque is applied, a phase difference (lost motion), as described later, develops between the two rotors. This phase difference enables torque to be transmitted while maintaining synchronous rotation.
If the transmitted torque exceeds the maximum transmissible torque of the magnetic coupling, the two rotors lose synchronization and slip relative to each other. This slip characteristic can be utilized to help protect machinery from overload.

4. Lost Motion

What Is Lost Motion?

In magnetic couplings, Lost Motion refers to the phase difference (rotational displacement) that occurs between the input and output sides. When torque is transmitted through a magnetic coupling, a phase difference develops between the input and output sides according to the applied load torque. This phase difference generates a magnetic restoring torque (a torque that acts to return the phase difference to zero), and this restoring torque is what enables torque transmission.

Zero Phase Difference

Please refer to Figure 1.
For simplicity, the following explanation uses a simplified 8-pole model. 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 couplings transmit torque by generating a phase difference between the input and output sides under load. This phase difference creates the magnetic restoring torque required for torque transmission. In other words, when the phase difference is 0°, no magnetic restoring torque 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 magnetic restoring torque that acts to reduce the phase difference. 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 torque. Consequently, the maximum transmissible torque is achieved at approximately 22.5°. If the load torque increases further, synchronous rotation can no longer be maintained, causing the input and output sides to lose synchronization and 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 coupling. 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 couplings transmit torque by utilizing the magnetic restoring torque generated by this phase difference.
• As the load torque increases up to the maximum transmissible torque, both the phase difference and the corresponding magnetic restoring torque 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.
• Lost Motion is an inherent operating characteristic of magnetic couplings that occurs as torque is transmitted.

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Potential Applications of Magnetic Couplings 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 mechanical components, as well as lubricant mist, can reduce production yield.

Solution:
Magnetic couplings transmit torque without physical contact, eliminating wear particles from contact surfaces. They provide clean power transmission and help improve production yield by reducing particle generation.

2. Reduced Maintenance and Downtime

Potential Challenge:
Wear of mechanical components and periodic maintenance of shaft seals can result in equipment downtime and reduced productivity.

Solution:
Because magnetic couplings transmit torque without physical contact between the input and output sides, wear associated with direct mechanical contact can be reduced. In addition, power can be transmitted through a barrier, enabling seal-less designs that eliminate the need for dynamic shaft seals. These characteristics can help reduce maintenance requirements and equipment downtime 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 component replacement and other maintenance work.

Solution:
Since magnetic couplings transmit torque without physical contact between the input and output sides, wear associated with direct mechanical contact can be reduced. This can help reduce maintenance requirements associated with wear.

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 of a magnetic coupling are not physically connected, direct vibration transmission from the input side to the output side can be reduced compared with conventional mechanical couplings. In addition, the absence of mechanical contact between the input and output sides can help reduce vibration and noise associated with mechanical contact.

Medical Device Industry

1. Reduced Maintenance and Downtime

Potential Challenge:
Medical devices may require periodic replacement of worn components and maintenance of shaft seals, which can result in increased equipment downtime and higher maintenance costs.

Solution:
Magnetic couplings transmit torque without physical contact between the input and output sides, helping reduce wear associated with direct mechanical contact. In addition, power can be transmitted through a barrier, enabling seal-less designs that eliminate the need for dynamic shaft seals. These characteristics can help reduce maintenance requirements, 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. The generation of wear particles may increase the risk of contamination and add to the burden of cleaning and sterilization.

Solution:
Because magnetic couplings transmit power without physical contact between the input and output sides, wear particle generation associated with direct mechanical contact can be reduced. As a result, they provide clean power transmission and can 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 couplings transmit power without physical contact between the input and output sides, vibration and noise associated with mechanical contact can be reduced. They can 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, wear particles generated by mechanical components can become sources of product contamination, potentially leading to reduced product quality and product recalls.

Solution:
Magnetic couplings transmit torque without physical contact between the input and output sides, helping reduce wear particle generation associated with direct mechanical contact. This can help reduce the risk of product contamination caused by wear particles, 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 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 sealed product-side structure. In addition, because torque is transmitted without physical contact between the input and output sides, wear associated with direct mechanical contact can be reduced. These characteristics can help 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 couplings 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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FAQ

Q.
Is the performance of magnetic couplings affected by the ambient temperature?
A.
Yes. The transmissible torque of magnetic couplings varies depending on the ambient temperature and generally decreases as the temperature increases. The maximum operating temperature of our standard magnetic couplings is 80°C.

Q.
What materials can be used for a barrier when transmitting torque through a barrier with magnetic couplings?
A.
The barrier should be made of a non-magnetic material that does not significantly interfere with magnetic torque transmission. For metallic barriers, non-magnetic stainless steel can be used. If aluminum or copper is used, please consult us in advance, as these materials may affect product performance depending on the operating conditions. For non-metallic barriers, materials such as plastic and glass can be used.

Q.
Do magnetic couplings experience demagnetization over time?
A.
Yes. Some demagnetization occurs over time, but under normal operating conditions, it is approximately 0.1% per year.

Q.
What is the lead time for magnetic couplings?
A.
For standard products that are in stock, the lead time from order placement to shipment is approximately 2–3 weeks. For custom products and other cases, please contact us for lead time information.

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