CVT use in Agricultural Vehicles

Today’s farmers are more cost conscious than ever before. Fuel costs make up 15 to 20 percent of a typical crop’s total overhead costs and are the largest expense after seed, fertilizer and chemicals. Consequently, gains in fuel efficiency deliver measurable profit.

The Challenge of Managing Fuel Efficiency

The loads on a tractor’s drive train are constantly changing and adjustments to the gear selection and throttle position are needed continuously to balance the competing demands of fuel efficiency, productivity and quality control. As most farm equipment is engineered to be most fuel efficient at maximum load, whenever equipment is operated at less than maximum load, fuel efficiency begins to drop. Using a higher gear and lower engine speed can recoup some of this fuel efficiency loss, but not all of it. An automatic system with an infinite number of operating points is required to fully optimize fuel efficiency.

The Milner continuously variable transmission is able to adjust the ratio between its input and output speeds like a geared transmission does, but the MCVT does so in a “step-less” manner with the following benefits:

  • Ratio change can be done under load.
  • Ratio change occurs without the need to clutch and change gears, so there is no interruption of power delivered to load.
  • The prime mover (engine) can be set to run at the optimum rpm for power or fuel efficiency and the MCVT ratio controls the vehicle speed instead of the throttle setting controlling the speed.

Use of an MCVT Can Result in Significant Gains in Fuel Efficiency – How it Works

The use of an MCVT in a tractor helps to optimize the two primary operating modes: field work and transport. With the controls set for field work, control can be optimized to maintain consistent ground speed or power take off RPM, depending on the work being done. Fuel costs are reduced because digital control of both the engine RPM and continuous transmission ratio are constantly being adjusted to deliver the correct amount of power while maintaining a constant output speed. By using the MCVT, small changes in transmission ratio can be made because the machine is no longer restricted to a set of fixed gear ratios. The control system monitors the operating conditions and makes the adjustments, leaving the machine operator free to concentrate on other tasks.

For transport mode, ground speed is allowed to fluctuate within set limits while fuel efficiency is optimized. All of this is accomplished by a control system that constantly monitors the engine and transmission settings and updates them many hundred times each second. The system has all the control benefits of the field work scenario, with a different operating condition optimized - fuel efficiency.