Variator or Continuously Variable Transmission (CVT)

Overview

• The variator is designed to smoothly change the gear ratio.

Components of the Variator

• Movable Cheeks:
  • Located on both front and rear pulleys.
• Spring Support:
  • Constantly supports the movable cheeks.
• Belt:
  • Has a V-shaped profile.
  • The sides act as the working surface.

Operation

• Centrifugal Force:
  • Acts on the variator rollers based on crankshaft speed.
  • Higher crankshaft speed = stronger action on movable cheeks.
• Movable Cheek Action:
  • Rollers move away from the center due to centrifugal force, pushing the movable cheek.
  • Both cheeks converge, pushing the belt onto a larger radius on the front pulley.
• Belt Movement:
  • Front pulley pulls the belt towards itself.
  • Rear pulley cheeks diverge, moving the belt to a smaller radius, thus reducing the gear ratio from front to rear.

Decreasing Engine Speed

• When engine speed decreases:
  • Centrifugal force on rollers decreases.
  • Rear pulley spring drives the belt to an increased radius.
  • Softer spring = lower crankshaft speed needed for rollers to return.
  • Movable cheek of front pulley returns, achieving minimum radius and increasing gear ratio.

Centrifugal Clutch

• Function:
  • With increasing speed, rear pulley pads diverge from the rotation axis.
• Torque Transmission:
  • Pads move apart and press against the clutch housing.
  • Torque is transmitted from variator to gearbox.

Conclusion

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