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NTN Develops "Monoring™ CVT" for Automobiles
with Unique Simple and Efficient Construction

NTN Corporation has developed the Monoring™ CVT (MR-CVT), a continuously variable transmission (CVT) for automobiles with a unique construction.


Automatic transmissions for automobiles are gaining more gears, in order to efficiently transmit engine power and smoothly shift gears. Meanwhile, the continuously variable transmission (CVT) is the ultimate in multi-gear transmissions, being capable of an infinite number of speeds. CVTs enable high efficiency, low energy consumption, and extremely smooth driving. In recent year, commercial applications of toroidal and metal-belt CVTs have been developed. However, these CVTs have complex structures, and require hydraulic pressure for shifting. For this reason, they have such issues as power loss and loss of efficiency at normal speed ranges.

The Monoring™ CVT developed by NTN has a unique structure that previous types never have: the gear mechanism consists of a small number of parts, and it does not require external hydraulic control apparatus for shifting. The CVT operates on the same principle as a metal-belt CVT, with the width of V-pulleys changed by means of an electric actuator, shifting gears by changing the contact point between the toothed ring and V-pulleys. While both the toroidal and metal-belt CVTs change speed by both the input and output of the gear mechanism (variator), the Monoring™ CVT only continuously changes speed of one side (input), with a fixed-speed gear transmission on the other (output). This makes the structure simple and highly efficient.


[Feature]

  1. Simple structure
    • Simple structure consisting of toothed ring and V-pulleys
    • No hydraulic pressure or other special mechanisms required to shift gears
  2. High efficiency
    • Designed for high efficiency in normal ranges, achieving 93% transmission efficiency




<Features>

New simple and efficient CVT mechanism
  • Use of toothed ring in place of metal belt
  • Self adjustment of pressing force in accordance with load

<Key Technologies>

  • Structural Features (see cross section)

    The outer periphery of the gear unit has a simple construction consisting of a toothed ring and V-pulleys. Although the toothed ring and V-pulleys must be pressed together with great force in order to efficiently transmit the drive force, the construction passively latches the V-pulleys to the toothed ring to transmit the drive force. There is no need for a hydraulic mechanism or the like to obtain pressing force.

  • Gear Shifting (see gear shift operation diagram)
    When speed increase to maximum:
    Distance from V-pulleys decreases Outer surface of V-pulleys contacts toothed ring.
    When speed decrease to maximum:
    Distance from V-pulleys decreases Inner surface of V-pulleys contacts toothed ring.


Cross-section drawing


Gear-shift operation


Transmission Efficiency: Prototype for light vehicles

Note: Efficiency of full toroidal quoted from in-house data

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