Fuel Efficiency Focus for Mobile Hydraulics

The ability to integrate these systems and maximize power use has allowed Caterpillar to downsize its engines and move to more power-dense solutions, which means burning less fuel. To make systems both simple and more effective, the company has completely changed the way the operator interacts with the machine itself in the new K Series wheel loaders.

"The K Series is the only wheel loader in the market that is solely joystick operated, and we are soon planning to introduce a new XE power train option that is a game changer, as well," said Weiss. "The hydromechanical transmission system that we have developed in the XE model is producing phenomenal fuel savings and simplicity for operators, who can operate the machine's propulsion with merely a stop pedal, a go pedal, and the steering joystick."

Competing machines have used "thumb sticks," he said, but their implementation and operation is not widely accepted in many applications that involve roading the machine. With the Cat K Series medium wheel loaders and innovative work with the joystick and electrohydraulic systems, Caterpillar can remove the steering wheel and provide exceptional responsiveness through an exclusive force feedback system. As the machine's ground speed increases, for example, the integrated force feedback through the joystick improves steering control and comfort.

"The new design has improved safety not only because visibility is much better without the steering wheel, but because it also allows the operator to become much less fatigued, especially in truck-loading applications," said Weiss. "Before, the operator would need to turn the steering wheel left and right, then dump, and repeat the process all day."

A key for the electrohydraulic systems within the new XE integrated power train is that the machine can do a lot of thinking for the operator. For example, if the operator stops while the machine is moving up a grade, the machine doesn't start rolling backward. The system knows that would be an uncommanded movement. An operator who wants to go backward can select a transmission direction change. Otherwise, the system stays put on the grade.

Another example is intelligent braking when going downhill. The system saves energy by braking on its own to maintain constant ground speed. The design goal was to think through various operating conditions, get the machine to understand what it is doing, and modify its behavior to produce the most efficient performance.