Planetary gear PTO unit with a hydraulic control, work vehicle comprising the same and PTO torque estimation

A working vehicle comprising a power take-off (PTO) unit comprising:

• a planetary gear having a first shaft for connection with an engine of the work vehicle;
• a PTO spline connected in power transmission to the planetary gear and defining a gear ratio with the first shaft;
• a hydrostatic transmission driven by the planetary gear to control the gear ratio;
• a pressure sensor unit for sensing a differential pressure across a loop of the hydrostatic transmission;
• and
• a control unit programmed to calculate:
• a differential pressure drop in the loop on the basis of an actual kinematic status of the planetary gear and from a calibration mathematical model representing an unloaded functioning of the PTO spline;
• and
• a PTO spline torque from a further mathematical model based on the pressure drop, on pressure signals from the sensor unit, and on kinematic or hydraulic factors of the planetary gear and the hydrostatic transmission.

A method to estimate torque at a power take-off (PTO) spline of a PTO unit for a work vehicle comprising:

• a planetary gear having a first shaft for connection with an engine of the work vehicle;
• a PTO spline connected in power transmission to the planetary gear and defining a gear ratio with the first shaft;
• a hydrostatic transmission driven by the planetary gear to control the gear ratio;
• and
• a pressure sensor unit for sensing a differential pressure across a loop of the hydrostatic transmission,
• wherein the method comprises steps of:
• calculating a differential pressure drop in the loop on the basis of an actual kinematic status of the planetary gear and from a first mathematical model representing an unloaded functioning of the PTO spline;
• and
• calculating the PTO spline torque from a further mathematical model based on the pressure drop, on pressure signals from the sensor unit and on kinematic or hydraulic factors of the planetary gear and the hydrostatic transmission.