NTN Develops Fluid Dynamic Bearing That is Capable of Forward/Reverse RotationFebruary 18, 2025
- Reducing customer's manufacturing costs by eliminating the need to confirm the direction of rotation
- Featuring excellent quietness, low vibration, and low torque immediately after startup!
NTN Corporation (hereafter, NTN) has newly developed a fluid dynamic bearing that that is capable of forward/reverse rotation. It eliminates the need to confirm the direction of rotation when assembly that the conventional fluid dynamic bearing requires and features quietness, low vibration and low torque compared to the oil-impregnated sintered bearings without dynamic pressure grooves, contributing to improvements in quietness and energy saving of compact motors and actuators, and reducing customer's manufacturing costs.
Background of development
Oil-impregnated sintered bearings without dynamic pressure grooves that is capable of forward/reverse rotation or rolling bearings are mainly used in compact motors and actuators for applications such as home appliances and automotive electronics.
In recent years, the use of fluid dynamic bearings with excellent quietness and low vibration, low torque is increasingly expanding towards the realization of carbon neutrality. However, as the conventional fluid dynamic bearings can rotate only in one direction, they require the need to confirm the direction of assembly which causes increases in customer's manufacturing costs.
We have newly developed the fluid dynamic bearing that is capable of forward/reverse rotation by optimizing the surface texturing*1 of bearing inner diameter. With this product, we can provide bearings with excellent quietness, low vibration, and low torque compared to the conventional oil-impregnated sintered bearings without dynamic pressure grooves as well as reducing customer's manufacturing costs by eliminating the need to confirm the direction of rotation when assembly.
- Unevenness to be machined on the bearing's sliding surfaces to generate dynamic pressure during bearing rotation.
Developed product
Features
| 1. Capable of forward/reverse rotation |
The shape and depth of the surface texturing are optimized through simulation analysis. Symmetry in the surface texturing enables dynamic pressure to be generated in forward/reverse rotation. The process of confirming the bearing assembly direction is no longer necessary, contributing to customer's manufacturing cost reduction. |
|---|---|
| 2. Quietness and low vibration | Optimized surface texturing generates hydrodynamic pressure immediately after rotation to achieve 100% oil film formation rate. Even during startup, when typical bearings without dynamic pressure grooves tend to come into contact with the shaft, the developed product is non-contact immediately after startup, resulting in excellent quietness and low vibration from the startup phase. |
| 3. Low torque | Optimized surface texturing reduces torque by forming an oil film immediately after rotation, and even during normal rotation, torque is reduced by 10% compared to typical bearings without dynamic pressure grooves. |
NTN will propose and sell oil-impregnated sintered bearings including the developed product to meet a wide variety of customer needs globally and contribute to further quietness and energy savings in home appliances and automotive electronics.
Applications
Motors for home appliances and automotive applications, actuators for automotive electrical auxiliary equipment, cooling fan motors
Comparison of oil film formation rate, torque, and vibration value between the developed product and a typical oil-impregnated sintered bearing without dynamic pressure grooves
(Click to zoom)
About oil-impregnated sintered bearings
There are two types of bearings: rolling bearings that use rolling elements such as balls and rollers, and sliding bearings that do not use rolling elements and receive shaft rotation with sliding surfaces. As for sliding bearings, NTN offers plastic bearings that use plastic material and the “BEARPHITE” series of oil-impregnated sintered bearings where lubrication oil is contained in porous sintered metal body. Oil-impregnated sintered bearings are divided into two types: bearings without dynamic pressure grooves that contact directly with shaft, and fluid dynamic bearings which does not contact with shaft by forming an oil film around the entire bearing clearance due to oil pressure generated by surface texturing of bearing inner diameter.
NTN has been offering the “Hydrodynamic BEARPHITE*2” with dynamic pressure grooves in bearing inner diameter as fluid dynamic bearings. They are widely used in fan motors for mobile devices such as PCs which requires quietness.
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Press release on July 12, 2023: NTN Expands sales of Hydrodynamic BEARPHITE
https://www.ntnglobal.com/en/news/new_products/news202300057.html
Press release on October 19, 2023: NTN Develops World-smallest Hydrodynamic Bearing “Hydrodynamic BEARPHITE”
https://www.ntnglobal.com/en/news/new_products/news202300081.html
Bearing classification
Oil film and oil movement of Hydrodynamic BEARPHITE (left) and
typical oil-impregnated sintered bearing (right)
Comparison of NTN's oil-impregnated sintered bearings
| Merits | Oil-impregnated sintered bearings without dynamic pressure grooves BEARPHITE | Fluid dynamic bearing | |
|---|---|---|---|
| Hydrodynamic BEARPHITE | Developed product | ||
| Cost*3 | Good | Average | Good |
| Quietness | Average | Excellent | Good |
| Low torque | Average | Good | Good |
- Customer's manufacturing costs for assembly
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