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NTN Corporation Develops Double Row Bearings for Electromagnetic Clutches with World Class Seal

NTN has developed a special double-row bearing for electromagnetic air conditioner clutches. This bearing uses a seal with extraordinary performance that does not allow internal bearing pressures to increase seal drag.


The electromagnetic-clutch bearings for car air conditioners are used in environments susceptible to moisture, dust, and other foreign substances. For this reason, these bearings must use a high quality seal in order to ensure that the bearing lasts for its rated lifetime.


One method to improve seal effectiveness is to increase the pressure on the seal. However, this causes higher friction on the sliding surface, and increases the rotating torque. Increased seal drag can also occur when the internal pressure falls due to a change in bearing temperature. This condition is called adsorption.


Using the latest FEM engineering tools, NTN has optimized the contact angle and tip shape of the seal lip, along with the surface finish between the seal and slider. These changes help obtain a stable seal, from low to high rpm, without increasing rotating torque. Seal drag adsorption was an issue that was resolved through an innovative design shape. The new seal can also be used with thin-wall bearings (bearings whose cross section height is about 70% of conventional bearings). This helps satisfy the demand to reduce product size.


With an increasing demand for car air conditioners in Europe and Asia, NTN Corporation has developed these bearings to not only provide excellent sealing characteristics at high rpm, but helpas a product to contribute to develop more compact car air conditioner designs.


[Features of the Newly Developed Seal]

  1. Improved dirt and moisture resistance
    • 1/10th the infiltration of dirt and moisture of conventional products
    • Maintains dirt and moisture resistance at high rpm (10,000 rpm)
    • Also supports thin-wall bearings (cross-section height about 70% of conventional products)
  2. Low startup torque
    • Prevents seal adsorption due to changes in ambient temperatures and conditions





[Customer Requirements]

Construction design to prevent seal adsorption, yet ensuring critical sealing characteristics
  1. Improved dirt and moisture resistance
    • 1/10th the infiltration of dirt and moisture of conventional products
    • Maintains dirt and moisture resistance at high rpm (10,000 rpm)
    • Seal also supports thin-wall bearings (cross-section height about 70% of conventional products)
  2. Rotational torque characteristics
    • Improved resistance to dirt & moisture, while maintaining the same rotational torque as conventional products
    • Prevents seal adsorption, and avoids increase in startup torque

[Goals]

<<Improvements to Seal Design>>

1. A unique seal shape prevents seal adsorption

→Result: Prevents startup torque due to seal adsorption when bearing's internal pressure is low!

2. Optimized the contact angle and tip shape of the seal lip

→Result: Maintains optimum seal contact and low rotational torque as conventional products at all speeds ranges used (0 to 10,000 rpm)

3. Optimized seal sliding surface and surface finish

→Results: Prevents dirt & moisture from entering the bearing!

<<Seal Performance Evaluation>>

<<Seal Adsorption Evaluation>>

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