CTI Mag: A Beltless CVT Technology that really Works

A Beltless CVT Technology that really Works

Dana’s VariGlide® planetary variator is a CVT innovation with unique benefits and fewer drawbacks

Patrick Sexton, Director of Engineering, Light Vehicle Driveline Technologies, Dana Incorporated

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Issue: #December 2017

With Dana’s VariGlide® beltless variator, the promise of a versatile, modular continuously variable transmission (CVT) has been realized. Offering higher durability and fuel savings than competitive belt technologies, VariGlide technology delivers a CVT without the traditional CVT compromises.

Although evolutionary advancements in belt-based CVTs have taken place over the past decade, now a significant breakthrough in CVT technology is setting new standards in fuel economy, performance, controllability, and noise, vibration, and harshness (NVH). The scalable design coupled with the simple, passive mechanical clamping system makes VariGlide technology a significant departure from tradition.

Plus, the VariGlide variator is the only CVT technology capable of packaging within existing rear-wheel drive (RWD) package envelopes.

With the potential for greater fuel savings than competitive belt technologies, Dana’s VariGlide beltless variator represents a logical CVT technology choice for original-equipment manufacturers (OEMs) seeking 2025 fuel economy target solutions for applications including small front-wheel drive (FWD) passenger cars, RWD pickups, and allwheel drive (AWD) sport-utility vehicles (SUVs).

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Unlike conventional CVTs, the VariGlide® variator is compatible with rear-wheel drive vehicle architectures.

The VariGlide variator is easy to control and insensitive to slip induced damage. The high-pressure pump typically associated with high parasitic losses and complex control strategies required for belt CVTs has been eliminated.

The VariGlide variator operates as a traction drive. When the fluid at the contact patch experiences high pressures (>1GPa), it behaves like an elastic solid, enabling torque transfer. Speed ratio is controlled by modulating the relative contact diameters between input and output rings. The system uses skew shifting to minimize shift energy requirements and maximize stability. Ratio control is achieved using a lowenergy electrical or hydraulic actuator.

With regard to hybrid and electric vehicles (EV), VariGlide technology has the potential to right size the motor and power electronics, optimizing overall system efficiency and energy recuperation, while boosting performance and maximizing operating speed range. The simplicity and precision of the VariGlide-equipped hybrid power path offers enhanced electric motor operating efficiencies, energy economy improvements, and the potential to use a smaller internal combustion engine. For pure electric systems, the VariGlide variator eliminates the need for a mode shift relative to traditional 2-speed systems.

To develop the variator for volume production, Dana built a dedicated, 45,000-square-foot technology center in Cedar Park, Texas, U.S., where customer prototypes are designed and tested. This advanced facility houses design, analysis, simulation, controls, and manufacturing teams dedicated exclusively to refining VariGlide technology for production applications.

The on-site test equipment accommodates applications up to 400 hp, featuring low-inertia motors equipped with engine-firing pulse simulation and tilt and roll capabilities. A cold chamber, AWD chassis dynamometer, and metallurgy and metrology labs are available on-site and used to support the product validation process.

Being uniquely compatible with RWD configurations is another attribute of VariGlide technology. To showcase the variator’s performance in the RWD segment, Dana is developing the next-generation test vehicle equipped with a 4-mode VariGlide transmission architecture designed to demonstrate drivability and fuel economy. The unique characteristics of the selected powerpath enable torque transfer during the mode shift to enhance drivability and acceleration.

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