CAN System for Hydraulics

Husco Intl.'s INCOVA technology represents a radical departure in the way hydraulic systems operate, offering OEMs and their customers improvements in six critical areas -- productivity, efficiency, controllability, reliability, safety and flexibility -- without adding to the total cost of the vehicle.

Husco began working toward what would become INCOVA (Intelligent Control Valve) seven years ago, when the R&D department brainstormed what it would take to create a hydraulic system that would be completely different. In the past, improving one aspect of the hydraulic system meant sacrificing another.

"By first starting with a clean sheet of paper and focusing on how to increase the six critical customer areas," says Chris Kolbe, vice president of sales and marketing, Husco Intl., Waukesha, WI, "we were able to identify the spool as a main limitation in preventing any significant change."

Because the orifices in a spool valve are tied to each other, there are no degrees of freedom as they cannot operate independently. The old spool valve was tossed onto the scrap pile.

After further development, in its place went an intelligent valve comprised of four independently controlled Electrohydraulic Poppet Valves (EHPV), in a layout similar to a Wheatstone bridge electronic circuit. The zero-leakage EHPVs provide bi-directional metering and metering modes.

"The real breakthrough was the zero-leak proportional control poppet valve which provides for independent meter-in meter-out operation," says Kolbe. "We worked on its development for a long time." The EHPV was completed and patented about three years ago. It's the hardware-enabling piece in the system, but the software is really the heart of the system.

"Once you go to electronics in a hydraulic system all of your customized controllability is in the software. This trend is changing the industry in the same manner INCOVA is altering the way Husco operates. "Now we have more patents on software than we do on our hardware," says Kolbe. "We have grown our staff of engineers who are focused on electronics and controls design significantly, where previously the great majority of our staff was mechanical engineers."

INCOVA's distributed electrohydraulic configuration is enabled by an integrated controller containing transducers which measure the pressures at the cylinder. This measurement allows the system to tell the pump what the pressure should be, enabling the system to provide electronic load-sensing and pressure compensation.

The distributed INCOVA valves are mounted out on the cylinders, eliminating more than 50% of the fittings and hoses that are required on a traditional hydraulic system. One of the benefits to this is the reduction of pressure loss in the hoses.

"At the end of a telehandler boom you'll have a cylinder for the fork," says Kolbe. "The flow has to travel from the pump through all that hose to get to the control valve." With the INCOVA system hydraulic fluid can be routed from one side of the cylinder directly to the other, travelling less than a foot. "It's the same idea as if you plug in about 200 ft. of cord to run a weed whip, it won't get enough power to operate. You can lose a lot of efficiency throughout the length of the hose."

Because hydraulic oil is going from one side of the cylinder to the other, the pump is not required to supply as much oil. The pump doesn't need to be as big, less heat is generated, and the entire system can require less oil.

Distinct advantages

With a changing workforce and the reduction of expert vehicle operators, electrohydraulics are increasingly being used to automate functions that could only be achieved by an expert operator in the past. "Manufacturers have been trying to utilize electronic-controlled hydraulics for a long time," says Kolbe, "but the problem is it has been very expensive. The INCOVA system reduces the system complexitity and cost by reducing the number of components, fittings, hosing, vehicle structure and horsepower requirements. The cost impact of adding electronic controls is nominally equivalent to pilot controls." Plus, INCOVA can increase customer value in six critical areas: