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Compact, Light-Weight "In-Wheel Motor Type Axle Units"

NTN Corporation has developed compact, light-weight "In-wheel motor type axle units" made up of reduction gear, motor, and hub bearing as the drive unit for electric automobiles.


In recent years, due to environmental problems, the development of fuel cell automobiles and electric automobiles has accelerated. As one drive system for electric automobiles and fuel cell automobiles, there is the structure called "in-wheel motors" with a motor built into each wheel. Compared to the system in which the motor is mounted in the car body, the in-wheel motor system has the advantages of superior space utility, for example greater ease in securing space inside the passenger compartment, and improved vehicle stability thanks to controlling the drive force at each wheel individually. On the other hand, deterioration of driving stability and ride comfort accompanying the increase in unsprung weight are problems and it is necessary to reduce the weight.


The "In-wheel motor type axle units" developed by NTN obtain a high reduction ratio in simplex, reduce the weight of the reduction gear by using a high-efficiency cycloid type reduction mechanism, and also use an axially compact axial gap type permanent magnet synchronous motor. Furthermore, by making hub bearings, which are NTN's main product, into a unit with the reduction gear and motor and optimizing the design, a compact, light-weight, high-efficiency in-wheel motor type axle unit is achieved.


[Features]

  1. Smaller size and lighter weight thanks to integrating into unit with hub bearing
    • Reduction gear output shaft and hub bearing integrated into one piece
  2. Highly efficient reduction gear that can rotate at high speed
    • A cycloid reduction mechanism is used with which high reduction ratios can be obtained in a compact size.
    • Use of roller bearings in the contact section within the cycloid reduction gear
    • The maximum rotational speed is raised through the use of counter-weight vibration due to the imbalance of inertial force.
  3. Motor made thinner
    • The combination with a reduction gear with high reduction ratios made the motor smaller and lighter weight.
    • The unit is made thinner through the use of a compact axial gap motor in the axial direction.

[Photograph]

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