Continuously variable transmissions (CVT) are becoming more commonly available in vehicles, including agricultural tractors. These transmissions, in combination with electronically controlled engines, provide the capability to smoothly change the transmission ratio and engine speed (revolutions per minute or RPM) to maintain or reach a desired power output and speed. In order to take full advantage of the CVT, conventional systems for the controlling engine speed include a variety of operator controls, which are fairly complex and confusing to many operators. A major contributor to this complexity is the control of the engine speed. An operator may wish to set the range of engine speed based on factors such as PTO operation, hydraulic requirements, the noise signature of the engine, and fuel economy.
Conventional systems for controlling engine speed of an agricultural tractor with a CVT typically include a hand throttle and a spring-loaded foot throttle to set the desired engine speed, and include additional switches or knobs to set operating modes. In some operating modes, the systems vary the engine speed within certain limits to minimize fuel consumption or to optimize other parameters. The amount of engine speed variation allowed and the proper usage of the modes are often not well understood by the operators. This can result in less-than-ideal operation of the agricultural tractor and may negate the advantages of the CVT.
Thus, there is a need in the vehicle control system field to create an improved control system for a vehicle with a continuously variable transmission. This invention provides such an improved control system.