NuVinci^® CVP Technology

Better Performance. More Economy. Transit buses, government trucks and commercial vehicles share a common AC problem – namely that a belt driven AC compressor is undersized for the refrigerating capacity desired because installation of a larger compressor is limited by available package space in the existing engine compartment. Scroll compressors are one solution, but they can’t be spun fast enough on the existing belt line.
		AC Compressor with NuVinci drive.
A NuVinci DeltaSeries™ AC compressor drive improves AC compressor performance by decoupling the engine speed from the compressor speed, enabling the compressor to operate in its optimal range based on demand regardless of engine speed.  As a result, the NuVinci compressor drive delivers the ideal compressor speed all the time – optimizing AC operation and performance, thereby enhancing performance, increasing system efficiency and improving fuel economy.

At the heart of every NuVinci accessory drive is Fallbrook’s award-winning NuVinci continuously variable planetary (CVP) transmission technology. The NuVinci CVP is a new class of CVT transmission technology that acts as a power management system to control the speed and optimize the performance of the accessory drive. Unlike conventional CVTs, the NuVinci CVP uses a set of rotating and tilting balls positioned between the input and output components of the transmission that tilt to vary the speed of the transmission. Tilting the balls changes their contact diameters and varies the speed ratio. As a result, the NuVinci CVP offers a seamless and continuous transition to any ratio within its range.

NuVinci DeltaSeries AC Compressor Drives Provide:

• Increased compressor output at low engine speeds
• Reduced compressor speed during cruise improves fuel economy
• Flexible packaging
• Opportunity to rightsize AC compressors
• Reduce startup torque transients to clutch, compressor, accessory beltline, thereby reducing NVH
• Optimized, demand-based compressor performance during cruise and acceleration

Better Feel. Better Performance. Better Solution.

A NuVinci DeltaSeries AC compressor drive improves AC compressor performance at low engine speeds, with minimal complexity, easy installation and low cost. It has also proven to improve fuel economy, by slowing the compressor speed down at higher engine speeds. The diagram below illustrates a thru-drive power path configuration. The AC compressor drive receives power from the belt, transfers it to one traction ring, through the planet balls, and out of the other traction ring. Tilting the balls provides a smooth ratio transition from overdrive to underdrive. In overdrive, the NuVinci accessory drive provides high compressor speeds at engine idle. In underdrive, it keeps the compressor from over-speeding at high engine speeds.

The NuVinci AC compressor drive enables control of output speed (see red line in chart below), independent of engine speed (the white line).  At engine idle, output speeds may be increased providing more performance from the compressor.  At higher engine speeds (such as accelerating from a stop or cruising), accessory speeds may be reduced, saving energy.  The NuVinci CVP also shifts quickly, help to smooth out transients.

The Result:

The graph below illustrates the improvements in both refrigerating capacity and volumetric efficiency that result from a NuVinci AC compressor drive.  The improvements in capacity will vary with compressor type, but the benefit to refrigerating capacity at idle can be as much as double for some compressor types.

Click here for a NuVinci DeltaSeries AC Compressor Drive datasheet (PDF) (contents of this page in printer format)

Click here to read the NuVinci Development Briefing:  A Continuously Variable Accessory Drive for Alternators and Other Engine-Driven Accessories

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